Ye of educated opinions, I respectfully call upon you for assistance!

[o1marc]

Originally Posted by sambulate

Dang, I hadn't considered that, but it's so obvious... You make a good case for a flat-nosed bus, for sure. I'm more concerned about total bus length than I am about inside dimensions, but this is definitely something to think about. I'd rather not have the engine inside, so FEs are still out. It makes sense to give REs as much consideration as dog noses.

Thanks so much for your input!

Just keep in mind with an RE you lose valuable rear entry. Side entrances may help, but keep that rear door access in mind.

[bp1791-unleashed]

Welcome to the forum! It looks like you've really done your homework, and you're now filling in the blanks and fleshing out the details from what you have learned and inferred. It also sounds like you have a realistic view of what you are getting into...

Originally Posted by BeNimble

I did not read all of this, but if you are towing something you have a legal speed limit
of 55mph and frankly going faster is just dangerous in a bus even if not towing.
This is in fact one of the reasons to have a motorhome vs trailer.
Increasing cooling capacity is not difficult, adding more HP is harder.
Decreasing the weight of the bus is something you might think about..

BeNimble, when I read this it surprised me, because I had never heard this before, and it prompted me to do some research, and I found this link:
https://rvnerds.com/resources/speed-limits-and-towing/. I see that California does indeed restrict a motorhome towing anything to 55MPH speed limit. Thank you for the new information, and prompting me to do some research.

Originally Posted by sambulate

There's a lot to think about here.

1. I'd just read that the MT643 was a better and stronger tranny than the AT545. I must have seen that it only had four speeds on the spec sheet I found on it, but apparently it didn't really register. It is, indeed, worth noting, as I'd rather have something with a wider range of gears.

Back when I got my first bus, I ended up with an AT545 because the other bus I was looking at had an MD3000 series transmission that I had no information about. Since I couldn't find information about it in time to bid or not, I passed on a better bus. The AT545 was an OK transmission. The primary reason for wanting an MT643 was that it had the lock up torque converter, where the 545 does not. Without lock up, there is extra heat generated, and dealing with hills makes that even worse.

Originally Posted by sambulate

One of the most difficult and frustrating parts of trying to figure out buses is trying to decipher which part (transmission, engine, tires, etc) is which. That is part of what is taking me so long to figure out how to shop for the right bus. That, and that sellers so seldom use anything but "Allison" or "Automatic" to describe the transmission on whatever bus they're selling!

Yes, you are correct, this is a frequent issue. A good seller will answer questions. Typically, a school bus has stickers or a plaque somewhere above the driver's seat with a lot of details about the build, including weights, axles, tire sizes, transmission info, and seating capacity. I would ask any seller to include pictures of those.

Originally Posted by sambulate

So..: Is the MD3060 the same as the Allison 3000? Or, is that just one model in the Allison 3000 series?
And in that vein, is the Allison 2000 just one model, or a series? If it's a series, which models should I look for in skoolies? (ex., 2100, 2200, 2500??)

This can be confusing, because people talk about a 2000 or 3000 as if it was a specific model, but it's actually a model series. The MD3060 is a 3000 series transmission, with 6 total gears but 6th is usually programmatically locked out on a school bus. There's someone that will unlock it for you though, look around on the forum for information. The 2000 series I believe is a 5 speed, and an improvement over the MT643. I believe both the 2000 and 3000 series have lock up torque converters (please someone correct me if I have this wrong).

Originally Posted by sambulate

5. The calculators tend to be pretty confusing, but I found this one that seems pretty basic and makes a leetle bit of sense. https://spicerparts.com/calculators/...rpm-calculator
I think I inputted the values of your bus correctly, though I had to guess at tire size based on what I measured on a bus here locally (40 inches from ground to top of tire).

Is there a way to take the value "275/80R22.5" and figure out what the "tire size" in inches is? That's been super confusing!

There's a calculator a member of the forum posted recently in another thread here: https://www.skoolie.net/forums/f37/l...tml#post401209. It's an excel spreadsheet, and one of the sheets within it has the gear rations for several transmissions that you can copy and paste into the first page. There is another sheet in there for Tire Sizes, where you can put in the tire size (295/75 22.5) and a squish percentage (guidance is provided above) which gives you the number of tire rotations per mile, which you can then take back to the first sheet. By using this calculator and my tachometer and speedometer, I've inferred that my rear end is probably around 6.10. I still need to get a better answer than "probably" so I know what I am working with.

Originally Posted by sambulate

I'm thinking about making another post about how to decipher (for us layfolk) the calculators that get into the meat of things. Also, a lot of the links to calculators that folks have posted here seem to be dead now.

That sounds like a good idea to me. It might be worthwhile consolidating links to calculators and seeing if Power Hungry would be ok with his calculator spreadsheet being on such a page. (my guess is he will say yes, since he already posted it in his thread).

[bp1791-unleashed]

(sorry for double-responding, still getting used to multi-quote and forgot to hit this one too, and didn't want to rewrite everything)

Originally Posted by sambulate

The Why: For a while, I’d like to travel (lots of places), park, work, repeat. And eventually, I want to find a piece of land on which I can park the bus and live in it while I put together a small community of homes built with natural materials (cob, straw bale, timber framing, etc). I just don't know where yet, and I want to look around a bit while schlepping the cats and dog along. I got plans, y’all.

This is a very good idea, and I've heard of a few others with similar plans. In my own case, the land is already there, I just need something to live in for a few years before building something more permanent, at which point the bus would become a camper.

Originally Posted by sambulate

Bus size and shape: I want something 2006 or older that is big enough for me, three cats, and a dog to live in comfortably (i.e., not a mid-sized), but not so huge that it's such a pain to find parking, or to maneuver: a shorter full-sized bus that is 35' or less.
I'd prefer a dog-nosed bus to keep the engine out of my living space and for ease of engine access, although I might compromise with a RE for the right bus.
I will be towing a 2012 Nissan Frontier Pro4X with a camper shell, which is (according to Google) just under 4400 lbs. It's a 4x4, so I may need to put it on a trailer to tow it. Not sure yet, but it will definitely be towed.
When it comes down to it, the engine, tranny, and rear end of the bus are most important.

Dog nose vs flat nose is very much a personal preference. As someone else pointed out, your living space in a dog nose will tend to be a smaller percentage of vehicle length than in a flat nose. For a front engine flat nose, you might find your cats enjoy laying atop the engine cover for the warmth. A rear engine tends to lend itself to a rear bedroom setup fairly handily. It's all a matter of where you want to make the tradeoffs.

I have a rear engine, flat nose bus that is 34' total. I have almost 30' of "behind the driver" space to convert. The rear engine compartment does take a few feet of that at floor to window bottom level, but it is clear to the back wall above that. My bus has the MD3060 transmission. Proper care and attention was NOT put into the selection of this bus.

You won't be unhappy with a 466 (mechanical or electronic) or an 8.3L Cummins. If you get the 466, especially the electronic version, you might want to check into the Beta program that Power Hungry is doing (the thread the calculator I linked earlier is within).

Driveline wise, I think I would focus hard on engine and transmission combo as changing one of those is a serious endeavor, and a huge time and money sink. It can be done, and has been done, but is a big project to jump into. Rear end re-gearing can be done by any competent medium duty to heavy duty truck shop. While certainly not cheap, it's not as expensive as an engine or transmission change.

As for serviceability of the engine... a dog nose has the mechanic working around the steer wheels and steering shaft, but everything is accessible from the outside. A flat nose front engine has the mechanic working around the steer wheels and steering shaft and having to do the majority of the work from inside through the engine access cover beside the driver's seat. Also, that area tends to get quite noisy and warm for the driver. A flat nose rear engine bus tends to have easier access from the wide open rear door, but there is a lot of stretching and squeezing involved. There are some rear engine busses that have access from the sides instead of the back, and I suspect they're a little more difficult to work on.

Originally Posted by sambulate

Engine: DT466 or 8.3 L, both wet-sleeved engines--and because I'll be towing. I'm not too worried about whether it's mechanical or electrical. I don't expect to find an 8.3L engine in one of the shorter full-sized buses. I imagine I'll end up with a DT466/E, and I'll be content with that.
I know there are other good engines out there (3126, T444E) but I’m trying to make it hard for any mechanics in my future to whine at me or charge me a fortune.

Good choices and good reasoning. I know some prefer mechanical engines, and others prefer electronic engines. There's a sweet spot of a few years with electronic engines and not much emissions stuff before nearly all the diesel manufacturers basically kept beta testing stuff in production vehicles. Personally, I'm just not that inclined to do much of my own engine work, so I prefer an electronically controlled engine where it's (potentially) possible to retune the engine with a simple (hah!) programming change. An electronic engine also makes it easier to add a "glass dash" with something like the BlueFire LLC software and hardware interface.

Originally Posted by sambulate

Tranny: I've got my heart set on a MT643, only because I don't believe I'll ever find a MD3060 in a bus as small as I'd like.
Further, I can't find much enough information about the Allison 2000 to suit me, though I have heard pretty good things about them. And I am a bit confused about whether a "2000" is also a 2100, 2500, etc? People seem to call the 2000 all kinds of things.

A retarder would be a huge bonus, as I am just as concerned (or more so) about getting DOWN the mountains as much I am about pulling the truck up them.

I already mentioned the 545/643 and 2000/3000 series points in the other response. I want to mention that while it's nice to find a bus with a retarder of some sort already installed, it is also possible to have them added aftermarket. I want to add one to my bus at some point. I recently learned about the KLAM retarder, which uses an opposing electromagnetic field to slow drive shaft rotation and does not cause any of the noise issues that exhaust braking does (and hence is legal to use in municipalities that declare use of exhaust braking is illegal). It looks like adding one would be relatively easy for a good MDT or HDT shop. Again, not cheap, but not impossible either.

Originally Posted by sambulate

Brakes: Air.

Tires: Yes, please. (I know to look at date codes--less than 10 years old, and for cracking.)

Air brakes for sure!

For tires, I really would not trust any tire that is 7 years old or older.

I talked to a tire shop in Flemingsburg, KY last year about tires for my bus, and they recommended that the best time to get them is around june/july time frame, because that's when all the school systems get their tires replaced when they're "too old" or have too many miles. Many times they have plenty of life left in them but just aren't "good enough" for the safety for the kids. I'll be doing that this next summer. Their sister shop in Mount Sterling, KY recycles hundreds of bus tires each year that have plenty of life left on them.

Originally Posted by sambulate

Gear Ratios: I understand this topic--IF I don't think about it or look at it too directly. It took me a loooong time to figure out that there was a rear end ratio AND transmission ratio. Or gears. Or whatever.
SEE?
I know that the 7.17 rear end that is in my local buses are ridiculous (for towing, anyway) is NOT something I want. I also know that there is a fine line between torque, HP, speed, RPMs, etc, and that you often trade one for the other. I need something that will be reasonable for towing a bus both UP and DOWN large hills and mountains at reasonable speeds, respectively, and that will hopefully put me at 65 or 70 mph, at least, on the highway. And yes, I know these are school buses and that it's difficult to get the perfect set up. Depending on the price of the bus, I may have enough money to have the rear ends changed to something better. But of course, I'd much rather buy the bus already put together.

I'm still struggling with the gearing and ratios and such myself. My bus tops out at about 68mph, and I've learned that when it is at that speed, it's running all out at around 2400/2500 RPM. I'll be making changes to lower that RPM range.

Originally Posted by sambulate

If you skipped to questions, start here!

I've learned so much from this forum, but I am on overload and I need to start the serious bus shopping sooner rather than later. Thank you again, everyone, ahead of time. I am absolutely up for long and drawn-out explanations if you want to give them, though I’m not that great at interpreting technical jargon. Dumbing down is appreciated! Again, I can't tell you how grateful I am for your help!

My questions:

1. I'm looking at a 1997 International 3800 with a DT466/MT643 with retarder that was taken out of service in 2020. The mileage is about 268,000, and it's a dog-nosed style. I don't know the rear end specs. I am not able to physically inspect the bus because it's so far away. The age, especially, and mileage of this bus make me nervous, but if it's been in service all that time... What do you think?

Personally, this would be outside my comfort zone. 23 years in service sounds a little unusual to me. With that age and mileage, I would expect something to give soon, and potentially be an expensive repair. This is just my gut speaking, and this specific bus might be a hidden gem just waiting for you.

Originally Posted by sambulate

2. Should I think about searching for a newer bus with fewer miles?

I think with your specific set of criteria, there will be a limited selection, especially with the retarder thrown in. You'd be likely to find a good combination in one of the western mountain states, or even some place like KY or TN. I'd avoid a bus from OH due to salt. Same for most of the northeastern and midatlantic states north of Virginia. Virginia busses I would be careful with, there are some great ones, and some real rust buckets.

Being in too big a hurry to "get it and get started already" can cost you. The way I ended up with my own bus is a cautionary tale. I'm into it about $6500 or so at this point (8K with the conversion stuff as well) and it is finally mechanically sound enough I am comfortable driving it 700+ miles.

Should you search for newer busses or busses with fewer miles? Certainly, because it never hurts to have more options to choose from.

The 2000 or 3000 series is likely to be based upon the GVWR of the vehicle as much as anything. Some of the 2000 series can go up to around 28,000 pounds GVWR (and GCWR), others top out at around 26,000 pounds GVWR and GCWR. Above those values, you'll probably see a 3000 series transmission. For towing, I think you would want the 3000 series more than the 2000 series. See this page about the 2100/2200 series which shows applications, weight limits, and also mentions a 6th gear option: https://www.allisontransmission.com/...).pdf?sfvrsn=2

Originally Posted by sambulate

3. I haven't been able to tell for sure if the Allison 2000's are good for pulling (I think they are?). Also, I couldn't find out for sure if they have a 6th gear to unlock?

Yes, they're fine for towing as long as you stay within the weight ratings. Some models have 6th gear, some do not. Do not count on it having 6th gear unless it has already been unlocked.

Originally Posted by sambulate

6. If you had the choice between buying a bus in which you'd need to upgrade either your transmission or your rear end gear ratio to improve torque and speed, which would you choose?

Rear end for sure. And I think it's been mentioned that putting on different tire sizes can make a huge difference too.

Originally Posted by sambulate

I am genuinely sorry for the length of this post, but I appreciate whatever input you have.

Hah! You should see some of my posts, I do tend to ramble on a bit. Again, welcome to the madness, Sam.

Jim

[Truthseeker4449]

Originally Posted by sambulate

One of the most difficult and frustrating parts of trying to figure out buses is trying to decipher which part (transmission, engine, tires, etc) is which. That is part of what is taking me so long to figure out how to shop for the right bus. That, and that sellers so seldom use anything but "Allison" or "Automatic" to describe the transmission on whatever bus they're selling!

I understand, it's definitely not easy. Thankfully if you see an electronic shift pad, it will be a good transmission. One thing that I love about Thomas Buses is that this information is well displayed on the data stickers, below is one from one of my buses.



The engine line can be confusing, but ER means Rear Engined. 3126 refers to the Caterpillar 3126B and 210 is the horsepower rating. IIRC a Mercedes engine will be displayed as ME906. I don't recall what the 8.3 is referred to, but it seems they are usually rated for 250HP to 300HP.

A word of caution, the model numbers for the axles will not tell you the gear ratio.

So..: Is the MD3060 the same as the Allison 3000? Or, is that just one model in the Allison 3000 series?
And in that vein, is the Allison 2000 just one model, or a series? If it's a series, which models should I look for in skoolies? (ex., 2100, 2200, 2500??)

I'm honestly not sure what their numbering scheme is and it really is confusing. I've even seen 1000 be used refer to a AT545. A MD3060 is, to the best of my knowledge, indeed a 3000. I've also see MD3050 be used to refer to a model programmed for 5 gears. MD might refer to transmissions built for vocational use (which does include school buses) with certain internal parts and gear ratios.

2. Is there a way I can determine which years to which that would apply? Plate, spec sheet, call Allison, etc?

If it turns out I find a bus with a 2000 in which I cannot do this, would you still consider it still worth having for towing and highway travel?

You could try poking around in the Allison Unlock Threads, I'm pretty sure the topic was discussed there. IIRC the MD3060s came out in the mid to late 90s. The 2000s were not possible to upgrade until about 2004ish iirc. Even without 6th gear I would still consider it a fine transmission for towing a car and highway use with good gearing.

You could try calling Allison, but Allison hates modifying stuff for liability reasons. You might have more success calling a truck shop that is an approved dealer. You would most likely need a serial number for either or a picture of the transmissions data plate located on the side of the transmission.

5. The calculators tend to be pretty confusing, but I found this one that seems pretty basic and makes a leetle bit of sense. https://spicerparts.com/calculators/...rpm-calculator
I think I inputted the values of your bus correctly, though I had to guess at tire size based on what I measured on a bus here locally (40 inches from ground to top of tire).

Is there a way to take the value "275/80R22.5" and figure out what the "tire size" in inches is? That's been super confusing!

Try this one, I like it and have been using it for a few years.

https://tiresize.com/calculator/

I hope we're not overloading you with all the great information and opinions!

[Native]

Originally Posted by bp1791-unleashed

The 2000 or 3000 series is likely to be based upon the GVWR of the vehicle as much as anything. Some of the 2000 series can go up to around 28,000 pounds GVWR (and GCWR), others top out at around 26,000 pounds GVWR and GCWR. Above those values, you'll probably see a 3000 series transmission. For towing, I think you would want the 3000 series more than the 2000 series. See this page about the 2100/2200 series which shows applications, weight limits, and also mentions a 6th gear option: https://www.allisontransmission.com/...).pdf?sfvrsn=2

In the case of our Thomas bus, the Allison transmission is specified in a 30000 pound GVWR. The weight with no passengers was stenciled on the side near the fuel door and read 17500 pounnds. So it would seem the AT2000 does go p to 30000 pouds GVWR at any rate.

[EastCoastCB]

Originally Posted by Native

In the case of our Thomas bus, the Allison transmission is specified in a 30000 pound GVWR. The weight with no passengers was stenciled on the side near the fuel door and read 17500 pounnds. So it would seem the AT2000 does go p to 30000 pouds GVWR at any rate.

Yeah and my 5 window shorty with 545 has a gvwr of 29k.

[musigenesis]

Originally Posted by bp1791-unleashed

You won't be unhappy with a 466 (mechanical or electronic) or an 8.3L Cummins. If you get the 466, especially the electronic version, you might want to check into the Beta program that Power Hungry is doing (the thread the calculator I linked earlier is within).

As wanderlodge and others have pointed out, DT466Es from 2000-2003 are prone to corroded cylinder linings ($10K+ for the fix) if the correct antifreeze is not used. https://www.schoolbusfleet.com/forum...TOPIC_ID=21080

[tlzimmerman]

Originally Posted by Jolly Roger bus 223

zimmerman.
i have been told and researched this cause i have a 6.50 rear..
the rear end gear doesnt care how fast you are spinning it?
now putting rubber to the road.
when i did my research for what i have to make my 175 hp motor and 545 tranny with a 6.50 gear
the lower the numbers for rear gears to get my setup to highway speed i would lose pulling/towing capability.
for me its up motor HP and TRANNY when i change my 9r20 slit ring tubed tires to 22.5 tubeless with alcoa rims and new sneakers will only net 3MPH verses the money spent for more speed.
make sure your motor and tranny are up to the task before upgrade of rearend and tire size.
same motor and tranny rear gear change 6 to 4 you get a better road speed and might tow a little car depending on HP of motor and TRANSMISSION and of course a six to 3 change depending on your combination will make you slow off the line and eventually get you to interstate speed without towing anything?
but that is depending on motor HP/TORQUE and TRANNY?
the rear gears dont care how fast or slow you spin them?
the actual tire size doesnt care how fast they run?
for me 3000$ plus for upgrade 9/20 tubed to 10/22.5 tubeless rims and tire size upgrade to gain 3mph?
really?
3000$ to be able to go 51MPH in a 55MPH area instead of 49?
tire size does matter but the bigger picture is motor and transmission. not tire size and rear end gearing .
that is solely my opinion.

For speed of course. I'm not changing my tires for speed I'm changing my tires because many places won't work on a split ring anymore and I want any tire truck anywhere to be able to help me if I have problems with a standard size in stock tire they have ready. The extra speed is a bonus.

[RolesvilleMarina]

Some more random food for thought.

I couldn't find the bus I wanted, so I built my own. Towing a boat I had some weirder criteria (mostly fitting in ramps)

and so I chose what is prob the least liked bus

I have a 7.3 flat nose Vista bus and it came with the AT545. It was a VA bus and it has air ride, cruise, and was well taken care of. I paid $3500 for it. Top speed with the speed control removed was 57 at 2600...

so

I custom swapped out the AT545 with an Allison 2000 by myself in less than 3 weeks and working alone (physically, but a LOT of help from this forum and others)

I will say it wasn't so hard as I thought it would be. would you be able to pay a mechanic to do it? prob not, and I only can speak from my 7.3 world. I know nothing about buses, nor the other kinds of engines. But swaps can be done.. just research HARD as you already.

Our gear ratio is 4.78 and with the allison I hold on flat ground 65 MPH at 2000-2100 revs which is right the sweet spot she wants to be at.

our "climb speed" when I reach a mountain that requires me to downshift to 4 and keep revs at 2000 is 50mph which is not bad.

We just came back from the first trip in it and had to pass both up and down the dreaded fancy gap inclines.

had no issues, despite worrying myself to death.

In fact the trip was to a friends place who helped me design and build the hitch. We plan to tow, one at a time of course, one of the following items depending on where we go.

1. 22 ft sailboat - Including the trailer is around 2200 lbs loaded with gear
2. 17.5 stingray ski boat - weighs in around 2900
3. 1994 Jeep Wrangler YJ - yes the square headlights, so up yours to them haterz , and it weighs in at 2800 and would be flat-towed as it already has the hitch for so.

Inside the bus, in the stern is a 2001 Yamaha V-star 650
and on the stern outside on the mount is a Kawasaki 100 grocery/errand runner


My tires are low profile 255-70-22.5

Towing a 4k vehicle besides your engine and tranny combo make sure you build up your hitch well for the weight as well.

You are doing it right, by asking questions and doing research... The bus I wanted wasn't out there, so I built it custom instead (driveline wise)

cheers

[sambulate]

Originally Posted by o1marc

Just keep in mind with an RE you lose valuable rear entry. Side entrances may help, but keep that rear door access in mind.

Dang. That's true, too, and that is important to me.

[sambulate]

Originally Posted by MNbusboy

Not sure how you feel about traveling, but there is a bus auction closing just south of Denver. Some of the buses have great engine/transmission combos and are going super cheap so far!!

https://www.govdeals.com/index.cfm?f...DXyaJql3tykTfc

Thanks for the tip!

[banman]

Originally Posted by sambulate

Thanks for the tip!

You've been given some good advice by many here to sort through -- glad you're getting the magic I've found this site capable of.

A wee couple things to add:
The Allison 2000 debuted in ~2001-2002. My transmission(XMSN) tag says "2000" on it. But it is only one example of a series of xmsn models -- all the 2000 series will have the same outter case but different internals; stall converters, gear sets, pto set-ups.
I don't believe the 6th speed option existed until ~2005 so it's probably not economically feasible to convert my xmsn for example to a 6sp.

Likewise the MD3060 is one example of the 3000 series xmsn -- a dumptruck has need of some different internals than say a schoolbus...

Changing the rear-end is way less complicated than changing the xmsn, and you can find a reliable used 3rd member for ~$500 so a reliable gear change can be made for less than a $1000.

Not impossible but rear engine buses are usually harder to set up a tow hitch.

Figure the weight of your Xterra with camper shell is closer to 5000 lbs and will it really be empty or will you have "a few things stored in it..." when you're towing it? This to say I'd highly recommend the idea of flat-towing it to save weight and also if you're alone, it will be much easier to unhook a flat-towed (toad) and not have a trailer in the way as a large third object in your foot-print. Much easier to park the bus after dropping the toad compared to needing tractor-trailer parking to park a bus with a car-trailer behind it...

RE: tires and rpm calculators. You found you could simply measure the diameter of a bus tire to plug in a number to the gear/rpm/mph calculator.
It's more accurate to measure the radius of a tire from the ground up and multiply this by 2 to get the working diameter of the tire. Observe how flat the bottom of the tire is with the weight of the bus on it -- that doesn't change -- and the bus is only riding on the center of the hub down to that flattened area at any given moment in time -- so that's the actual working size of the tire.

See if there isn't a "maker space" near you where you can use tools for some of the parts of your project. There will certainly be one (or more?) in Raleigh. Might save you from buying some of the larger tools you don't need after you're done building. Might even provide a place to work on the bus...

You didn't mention it so -- high roof (6½ feet interior height) or low roof, only ~6' high.
If you're planning a roof raise regardless then this is irrelevant but otherwise I think it's crucial for interior comfort. A low roof bus should cost less at auction -- this could be to your advantage if you're a shorter person and need to accommodate taller peeps...

[RolesvilleMarina]

I see now you said you are near raleigh NC?

We live in Wake forest, which is top of raleigh

if you ever are in the area reach out and you are more than welcome to come and see ours in person and have a pint and a chat

[sambulate]

Originally Posted by tlzimmerman

1.

It depends on the bus....I LOVE That engine age range because you have either no electronics or simple electronics. Much easier to work on myself. Newer engines make me nervous. Without a good mechanic to be sure of problems before they start replacing parts they can nickle and dime ya. Is it a bad sensor or a bad wire ya know? In my experience older diesel engines are in general, more reliable....and nickle and dime you a little less. Not necessarily in major parts but on a new engine if you have a sensor malfunction and the bus wont run until the sensor gets replaced thats downtime and expense.

If this was a one owner bus and they have service records and it was taken care of and driven well you can hope for quite a bit more service, but on a used bus of unknown maintenance records I think 250k is a good number to start to expect to rebuild it. That isn't necessarily a horrible thing. It does take money but if you have a good mechanic at that point you have an engine that is a known quantity and you can take care of it.


2. Should I think about searching for a newer bus with fewer miles?

If it was me? I'd stick to a mid to late nineties bus myself. Thats my wheelehouse though. A DT466 is a great engine to have in that range because there are a lot of mechanics with a lot of experience with the engine. They are everywhere.

It certainly seems that the older mechanicals are simpler, and easier and cheaper to work on with fewer things to go wrong. I'd tend to agree with you about that. It just makes me nervous, looking at a vehicle over 20 years old.

3. I haven't been able to tell for sure if the Allison 2000's are good for pulling (I think they are?). Also, I couldn't find out for sure if they have a 6th gear to unlock?

I won't comment much as I am less of an auto trans expert. More gears is better and locking is good.

I couldn't find much on the 2000's 6th gear, either. I might call Allison to find out for sure.

4. Bus tire sizes are super confusing. I am especially interested in how to determine tire size for figuring out gear ratios and speeds and RPMs and stuff.

There are 2 common sizes you WANT to get to, plain old 11r 22.5 and low pro 295/75 11R 22.5 tires. 11r22.5 and the low pro variation are the road standard for big trucks and as such on the road are readily available about everywhere. The low profile version is a bit smaller than the large version. If you are wanting speed you want the taller tire, but where you are wanting to tow and do mountains you may want the smaller tire at the expense of a little speed. Keep in mind with ratios and the power you have and the weight you have its all trade offs. If you want to go faster you are gonna pull the hills harder. If you want to pull easier you won't go as fast. Ideally if you had 350 or 400 HP you just go tall and have plenty of power to pull it but in reality thats probably not what you will be working with.

Other sizes like 10.00 20 or 9.00 20 were the standard at one time. I've heard of a lot of busses coming with 10r/22.5 tires. Mine came with 9.00/20's. They are getting swapped for 11r22.5's. Worth the expense to me. It'll be about 2.4k for new rims and rubber.

This helps a bit.

5. As for rear-end gear ratios, what range would y'all consider reasonable for what I want to do? I've tried the online calculators you've posted, but they are confusing because I can't figure out what half the input values mean. (Tire size, bit also other things.)

That depends greatly on the engine and number of gears. If you have more gears a lower ratio will get you faster with taller tires. My bus has a split rear end. It has a 6 and 4.30 that I can switch between mated with a manual 5 speed. Really loaded down and towing with my taller tires 4.30 I think would be a little too tall, but most of the time I think its going to be perfect. I'll cruise at 65-70 and should have enough power with my engine, but a 5.9 cummins is pretty easy to turn up for a little more torque. It makes 170hp now, I'll probably put it to about 250 when its built out.

my advice would be set your sights at 60 mph towing your vehicle on the flat. Might seem slow but slow and steady is better than fast overheated and broke.

Your split rear end (uhhmmm... ) sounds complicated--but kinda cool. Did your bus come with that, or did you install it?

I'm also interested in how you "turned up" your 5.9 for more torque. Is that possible for the bigger engines, too?

6. If you had the choice between buying a bus in which you'd need to upgrade either your transmission or your rear end gear ratio to improve torque and speed, which would you choose?

Rear end. Way easier change.

That's what I'm gathering.

Thanks for your input, Zim. I really appreciate your answers!

[tlzimmerman]

2 speed rear ends are somewhat common in manuals transmission mid sized trucks.......especially in things like grain trucks that may drive heavy or light. I don't think they are too common in busses and I'm thrilled mine has one. The five speed manual and the 2 speed rear did me in....I had to buy it.

A 5.9 Cummins is a particularly interesting engine if it has a Bosch diesel pump. It's completely mechanical.....and if you know what you are doing and it has the Bosch pump it's pretty simple to change the fuel plate and some other adjustments in the diesel pump to give you more power. In other applications such as my bus the engine was tuned to lower power than it's capable of.

It's the mechanical diesel equivalent to modern diesels putting in a new computer file for more power. Often a diesel engine is offered in several different power levels with the same internals. Sometimes to turn them up you have to swap out some parts....and you should never put more power and torque to your transmission and drivetrain than it can handle.

I'm lucky....I waited for a bus I loved and it plopped in my lap. It's a pretty unique set up.

[sambulate]

Originally Posted by Brad_SwiftFur

My advice to you would be to find a bus that meets your highest priority checklist items first. Everyone may have a different checklist - for example, someone tall may require a 78" ceiling height (they don't want to do a roof raise), or a small family may want 40' length for maximum space, or someone wanting a garage will want a front engine bus with wheelchair lift on the rear. See where I'm going with this? In your case, you've already narrowed down what you want, so focus on finding a bus that meets those criteria. If the tires are old, well, they're gonna need replaced at some point anyway. If the rear end gears aren't what you want/need? Regear it (I just did this on mine). Bus has high miles? Engines can be rebuilt (at no small cost though, so this would be a big negotiation point).

You might luck out and find one that checks all the boxes, so to speak, but if it doesn't? Check as many as possible, then see how much it would take to check the rest.

It’s looking as if I’ll have to make some concessions for some things, like a short bus with pulling power and highway speeds. (I get the distinct impression I'm not the only one.) I was hoping to maybe find a cheap bus, then swap out a crappy tranny for a better one. But there are other things to think about (high-mileage engine overhauls, tires, miscellaneous parts that break, plus the actual conversion, etc), and that no longer seems like a reasonable way to go.

So yeah. What you said.

Although, ceiling height isn’t an issue at all. I’m 4’11”.

Tires for full size buses will come in 3 common sizes (yes, I know there are others but they aren't as widely used on buses). 10R22.5, 11R22.5 and "Lo Pro" 22.5, which will have 513, 492, and 507 revolutions per mile, respectively. Lower revolutions per mile will equate to more ground covered per engine revolution, also the same as effectively lowering your engine RPM for a given speed. Going the other way, a larger tire (lower revolutions per mile) will also increase your effective top speed, figure around 2 MPH for each tire size going up.

Now, having the tire revolutions per mile is only part of our equation. You'll need a couple other numbers - your rear end gear ratio and your transmission final drive ratio (or the ratio of your high gear). For an AT545, MT645 or most manual transmissions, this will be 1:1. For most overdrives it might be .75:1 or .71:1 (assuming 5th gear). Now, simply multiply all three of those together:

492*3.91*1 = 1932.72 engine revolutions per mile (also engine RPM at 60 MPH) (I used 11R22.5 tires, 3.91 gears and a 1:1 high gear in this example). You can calculate more from there, such as top speed, engine speed at a given road speed, and more. This was how I determined my choice of a 3.91 gear ratio, by the math it will give me a top speed of around 75, or around 2200 RPM at 7O.

The tire size formats are weird. Some look like 11R22.5, and some look like 295/75R22.5, like regular car sizes. Is there something that distinguishes one type from the other, or are they just weird?? I'm gathering that the 22.5 is the wheel/rim size?

You had me till the third paragraph down, but I lost you at the “(also engine RPM at 60 MPH)”.

Thank you for this, Brad. It's really helpful.

[sambulate]

Originally Posted by kazetsukai

Only thing I'd add is, if I was looking to travel, I'd just go with all new tires all around, unless all of them were under 3 years old. I wouldn't trust tires 6 years+.

I certainly will at some point, once I can afford it. It definitely sounds like the safest route.

For right now, though, I just want to be able to decide on one to bring home. Easier said than done...

[Brad_SwiftFur]

Originally Posted by sambulate

The tire size formats are weird. Some look like 11R22.5, and some look like 295/75R22.5, like regular car sizes. Is there something that distinguishes one type from the other, or are they just weird?? I'm gathering that the 22.5 is the wheel/rim size?

You had me till the third paragraph down, but I lost you at the “(also engine RPM at 60 MPH)”.

Thank you for this, Brad. It's really helpful.

I won't disagree about the tire size formats. The 22.5" is, as you guessed, the wheel size. Time for a history lesson!


Many years ago, at least in North America, tires were measured using inches and in the truck and bus world the 20 and 22 inch wheels were very common. There were 7.50x20, 8.25x20, 9.00x20, 10x20, 11x20 and a few other sizes (and several corresponding sizes for the 22's). Now, these were all tube-type tires and most used so-called split rims to facilitate tire changing. These could be dangerous if not reassembled correctly and some were known as "Widowmakers" for that very reason. As time and technology improved, tubeless truck tires came to be. But they were not interchangeable with the 20 and 22" tube-type rims, so to prevent this, the 22.5 and 24.5" rims were used. The various 9, 10, 11 measurements remained, however.


Other countries began using the metric system Way Back When, and this eventually included tire sizing. The 295/75R22.5 is an example of this, having a tread width of 295mm, an "aspect ratio" of 75% (this means the tire is 75% of 295mm from the ground to the rim when mounted) and of course the same 22.5" wheel.


A tire with "R" in the size indicates it is a radial tire. Otherwise it is a older style bias-ply (uncommon these days but up until the 70's and 80's this was 95% of tires on the road).


Sorry if my math stuff was confusing. What I mean is that calculating the engine revs per mile, as in my example 1932.72, translating that to engine RPM at a given speed. Since 60 miles per hour is the same as a mile a minute, it follows that, at that speed, that's how fast your engine will be turning.

[sambulate]

Originally Posted by bp1791-unleashed

Welcome to the forum! It looks like you've really done your homework, and you're now filling in the blanks and fleshing out the details from what you have learned and inferred. It also sounds like you have a realistic view of what you are getting into...

Thanks! Something tells me it will fully sink in once I buy a bus, get it home, and try to remove the first seat. Fortunately, I have TWO angle grinders!

BeNimble, when I read this it surprised me, because I had never heard this before, and it prompted me to do some research, and I found this link:
https://rvnerds.com/resources/speed-limits-and-towing/. I see that California does indeed restrict a motorhome towing anything to 55MPH speed limit. Thank you for the new information, and prompting me to do some research.

At least it's just one state that requires 55 MPH?! For a speed demon such as myself, this will surely be an adjustment.

But I went about 65 in the big truck, back in the day. I felt pretty safe doing it--unless I didn't for some reason, and then I slowed down when it was warranted, as you do. (I wasn't driving in California.) Once I start traveling (someday...?), I'll have to tape that list of states somewhere in the bus so I won't forget it.

Back when I got my first bus, I ended up with an AT545 because the other bus I was looking at had an MD3000 series transmission that I had no information about. Since I couldn't find information about it in time to bid or not, I passed on a better bus. The AT545 was an OK transmission. The primary reason for wanting an MT643 was that it had the lock up torque converter, where the 545 does not. Without lock up, there is extra heat generated, and dealing with hills makes that even worse.

I get you. I'd just about passed on the Allison "3000s," too, simply because I didn't know what they were. I'm glad I posted here.



Lockup was definitely a factor in my choosing the MT643, but I believe the MT643 is also a larger tranny than the AT545. (I would imagine that would make a difference somehow, not sure how.) Also, I was going off of what I read of forum member's experience with the MT643, as opposed to choosing based on specs. That it was four speeds didn't register with me when I read them. It's starting to come together now, tho.

I think.

Yes, you are correct, this is a frequent issue. A good seller will answer questions. Typically, a school bus has stickers or a plaque somewhere above the driver's seat with a lot of details about the build, including weights, axles, tire sizes, transmission info, and seating capacity. I would ask any seller to include pictures of those.

This can be confusing, because people talk about a 2000 or 3000 as if it was a specific model, but it's actually a model series. The MD3060 is a 3000 series transmission, with 6 total gears but 6th is usually programmatically locked out on a school bus. There's someone that will unlock it for you though, look around on the forum for information. The 2000 series I believe is a 5 speed, and an improvement over the MT643. I believe both the 2000 and 3000 series have lock up torque converters (please someone correct me if I have this wrong).

I've seen the plaque you're talking about.

I'm definitely going to compile a list of questions for Allison. They'll be thrilled...

There's a calculator a member of the forum posted recently in another thread here: https://www.skoolie.net/forums/f37/l...tml#post401209. It's an excel spreadsheet, and one of the sheets within it has the gear rations for several transmissions that you can copy and paste into the first page. There is another sheet in there for Tire Sizes, where you can put in the tire size (295/75 22.5) and a squish percentage (guidance is provided above) which gives you the number of tire rotations per mile, which you can then take back to the first sheet. By using this calculator and my tachometer and speedometer, I've inferred that my rear end is probably around 6.10. I still need to get a better answer than "probably" so I know what I am working with.

That sounds like a good idea to me. It might be worthwhile consolidating links to calculators and seeing if Power Hungry would be ok with his calculator spreadsheet being on such a page. (my guess is he will say yes, since he already posted it in his thread).

That Excel spreadsheet is absolutely helpful. I'll have to spend some time with it in the next day or so, to form a better understanding of it. I especially like that there is something called a "squish percentage!"

I'm trying to sort out all the great information I'm getting from you guys. Once I do, I'll see about doing a post about the calculators.

[bp1791-unleashed]

At this point in your research and search for a bus, you have so many possible permutations that it can be overwhelming.

Once you have your bus, all those permutations will collapse into a single definite option, and then you can dive deeper into just the options that you have, as they'll be more important to you than the ones you don't have.

It might help to give the different paramaters different weights of importance in your decision making, then apply that to any bus and see how well it matches.

Good luck,
Jim