School Bus Conversion Resources

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-   -   want just a bit more speed (https://www.skoolie.net/forums/f37/want-just-a-bit-more-speed-8553.html)

opus 06-03-2013 11:00 PM

Re: want just a bit more speed
 
Thats the correct answer. Rear axle number is on the plate above the door.

lornaschinske 06-05-2013 05:52 PM

Re: want just a bit more speed
 
Don't forget... the faster you go the longer it takes to stop. Once fully converted, a bus is a very heavy thing. 55 mph is okay on a highway. You may check to see if you have something mechanical, keeping your speed down. We had something on our bus. Had fantastic MPG's coming out west. MPG's sucked after David "fixed" the situation. He will be "unfixing" it. I really don't care to go faster. We need all the MPG's we can get. Diesel is so pricey!

JakeC 06-06-2013 07:43 AM

Re: want just a bit more speed
 
Quote:

Originally Posted by lornaschinske
Don't forget... the faster you go the longer it takes to stop. Once fully converted, a bus is a very heavy thing. 55 mph is okay on a highway. You may check to see if you have something mechanical, keeping your speed down. We had something on our bus. Had fantastic MPG's coming out west. MPG's sucked after David "fixed" the situation. He will be "unfixing" it. I really don't care to go faster. We need all the MPG's we can get. Diesel is so pricey!

Lol...sounds like me. I drove our bus 1 day before I figured out how to "fix" it (in a hotel parking lot in new mexico, lol).

travelinwithus 06-07-2013 12:57 PM

Re: want just a bit more speed
 
Just out of curiosity, what did they charge to reflash it?

opus 06-07-2013 05:27 PM

Re: want just a bit more speed
 
Wow, awesome! I dont have anything electronic so I never thought of that. You are right, 65 is fast enough in something heavy.

JakeC 06-08-2013 12:36 AM

Re: want just a bit more speed
 
I can clear 70 in mine, but that's at close to 2900 rpms. I don't mind driving it that fast out on the interstate, just don't like spinning the motor that fast.

OP, what size are your tires? I'm assuming by your gear ratio that you do not have 11x22.5 or similar. I would kill for 3.54 :) I'm just confused because with a 3.54 ratio and a typical 42" tire, at 55 your rpms would be INCREDIBLY low to be governed at. Glad the reflash did the trick for you!

Will 06-14-2013 12:43 AM

Re: want just a bit more speed
 
That 3.54 isn't a usual number for a school bus. A bus with a chip to flash isn't usual either. Most of you, like me, have to find a truck salvage yard with your desired pumpkin and swap them for it. I looked for 2 years and found a 3.73, eventually. It was very worth it.

To be honest, I have a Ford with a 7.3 Powerstroke. I'm glad my bus doesn't have that t444e motor. I just spent a million dollars on that Rube Goldberg injection system on my Ford truck. The Bosch inline pump engine is a Zen garden for me right now.

thrash 08-03-2013 12:48 AM

Re: want just a bit more speed
 
If you can find the make/model of your axle, chances are you can get a reman diff unit put in it by a truck shop. That's what I did. I have a 3.54 and its great, except when climbing mountains.

I weighed my bus and its right around 20,000 lbs. It's GVWRd at 26xxx and the axles are rated for 28,000.

I weighed it early on in the conversion process (all seats out, floor removed, bus otherwise basically empty) and I think it was around 16,000 lbs.

Point being, you can build a light bus. A bus meant for travelling high school football teams is carrying 40-60 adult sized kids (~200 lbs each) plus an interior, and is travelling at highway speeds.

JakeC 08-03-2013 03:43 PM

Re: want just a bit more speed
 
Do you know what hp your dt466 is? I have been wanting to put in 3.55's, but I want to be able to pull mountains decently. wondering if 3.73's would be better.

the_experience03 08-04-2013 08:08 PM

Re: want just a bit more speed
 
Quote:

Originally Posted by JakeC
Do you know what hp your dt466 is? I have been wanting to put in 3.55's, but I want to be able to pull mountains decently. wondering if 3.73's would be better.

The only solution to your problem is more gears than the average 4 speed skoolie transmission can provide..not that that's impossible. :lol:

opus 08-04-2013 10:21 PM

Re: want just a bit more speed
 
I'd be having me a 10 spd Road Ranger. Be a pretty cheap switch if you have a manual already.

JakeC 08-05-2013 10:55 AM

Re: want just a bit more speed
 
I know... it may have a road ranger some day. I keep looking at eBay even though I can't do anything right now, lol...

nevrenufhp 08-11-2013 02:37 PM

Re: want just a bit more speed
 
Quote:

Originally Posted by JakeC
I know... it may have a road ranger some day. I keep looking at eBay even though I can't do anything right now, lol...

Dont forget craigslist or a truck wrecking yard.

Hex 08-13-2013 10:11 AM

Re: want just a bit more speed
 
Quote:

Originally Posted by travelinwithus
Just out of curiosity, what did they charge to reflash it?

I got mine reflashed for free when they did the yearly inspection.

Jarlaxle 09-15-2013 08:11 PM

Re: want just a bit more speed
 
Quote:

Originally Posted by JakeC
Do you know what hp your dt466 is? I have been wanting to put in 3.55's, but I want to be able to pull mountains decently. wondering if 3.73's would be better.

I have 200HP, 4.11's and 11R22.5 tires...65MPH is 2100RPM. 3.55's would be WAY too tall! :shock:

Will 09-18-2013 09:20 PM

Re: want just a bit more speed
 
Only gears will get you what you want.

Will 07-24-2014 01:23 AM

Re: want just a bit more speed
 
Just finished a 4,200 mile trip from Indiana to Pike's Peak, Durango, Mesa Verde, and Grand Canyon. My bus is 185hp and has 3.73s replacing the 4.88s, and a 6-speed manual tranny. We did the long, flat stretches and went over the divide on a 2 lane road at 11,000 feet. We spent 3 nights at Mesa Verde pulling those climbs with the drop offs--and lots of other such things, so I can give you some insite on things about gear changes.

First, we did not get better mileage going from 4.88 to 3.73. We cruise at the same speed--normally 62mph--and get the same 12mpg. The engine is spinning more slowly and the bus is quieter and I feel a lot more calm. Our top speed with 4.88 was GPS 69mph. I can now do 78mph on a flat, and on the way home, through Missouri, Illinois and Indiana where it's largely flat, we were able to hold 73mph pretty much the whole way.

On really steep hills, there is no difference from the 4.88s and the 3.73s--same engine, same power--you will end up in a gear that the engine can pull in.

The reason I did the sap was for none of the above. I did the swap because with a 4.88 I was almost pegged on the tach just cruising down the interstate. When I hit a hill I would have to wait until I got down to under 50mph before I could downshift. On shorter trips I often drove the bus at 69mph with my foot on the floor and it really sucked to have to wait until I lost 20mph before I could go down into 5th. Also, I never used first gear with the 4.88--it was way too low. I drove this thing for 6 years thinking about how to make it better before I decided to do it. Now, if I decide to add power, I have the gears to run 95mph. It's already really fast for a bus. When I am zooming down the interstate with the pedal down doing almost 80 blasting past cars in an old school bus--that's funner than doing 140 on my Honda 919. I feel like the troublemaker on the old bus in grade school now driving the bus like I stole it.

Having an automatic will change everything from what I described. First, automatic trans people have an advantage when rating their products. They can rate something for 500ft# of torque even though it is only strong enough to endure 300ft#. The reason is, they will just program the tranny to downshift any time it sees over 300ft# and then the engine will let up on it. I have a Ford van with a Powerstroke and I run a Scangauge on it. I was pulling a 6,000# trailer and studying the gauge. The engine is rated at 425ft#, but anytime the gauge approached 100hp, the tranny would downshift. Under the specific conditions, 100hp was made by about 210ft# of torque. The tranny never let the engine lean on it very hard. From my experience driving Allisons, combined with my experience driving manuals with the same engines--Allisons also squirt out of the way when you apply torque to them. That means that even though you regeared it, the tranny will screw your efforts by downshifting to an even lower gear to protect itself from engine torque. You can still use all of your engine's power, but maybe half of its peak torque. This might not make any sense to you if you haven't driven a manual tranny in a large vehicle. These type of engines will lug down to about 1,700rpm while still pulling hard--they are actually riding UP the torque curve as they decelerate going up a hill. That's the nasty bit Allison doesn't want to expose their transmissions to. When you have your foot down--full fueling--and the rpm starts to drop, the torque starts to rise. The Allison downshifts, scooting out of the way. The downside is, you are always murdering the engine while saving the tranny. It's a key reason mpg is horrible with those old Allisons. If they were strong enough to keep a converter clutch (they don't have one) locked up, they would be my choice. They change all of your engine power into heat. I followed a new bus full of National Guardsman up the hill on Indiana 46 west from Nashville--it's pretty steep. My old 185hp manual bus makes that hill at 40mph. This new bus--what are they now--250hp?--made it up to 26mph and sat there in the way, struggling.

I would not bother regearing a bus with an auto. You will see maybe no return on that. I would spend the money on air ride. I put a Kelderman air ride on my bus last year and, wow, much quieter, much smoother and we haven't had an everything-goes-flying incident since.

opus 07-24-2014 09:55 AM

Re: want just a bit more speed
 
Great post. Nice to have the engine not screaming all the time, isnt it?

Booyah45828 07-24-2014 03:44 PM

Re: want just a bit more speed
 
That was a good post. Especially the part about the old allisons that are so far overrated it's not even funny. How new was the national guard bus? All the newer busses should have the electronic Allison 2000 series which are light years ahead of all the old hydraulic transmissions(at545, mt643, mt653, etc). There is no way that it should have been bogged down that much going up that hill. Now if I had a choice between an at545 and any manual I'd choose the manual, but with today's automatics that would be much, much harder of a choice to make.

Will 07-24-2014 10:17 PM

Re: want just a bit more speed
 
I don't know how old the Guard bus was. I didn't see the front, but it seemed new.

My wife tried to drive during the trip. I had been bothering her for years to let me coach her, but she wouldn't--probably thinking she could pick it up on the fly--how different from her old Tercel could it be? She drove from Des Moines to about 20 miles from Omaha and got confused trying to slow down. A lot of weight and not much power, plus, even though it is synchro, you still have to have an idea of gear/rpm matching because it doesn't forgive much difference in rpm when you are trying to let the clutch up. It's a lot of dam work in traffic, in mountains, in hilly areas etc. She did about an hour out of 78 hours. I had fun, after 7 years of driving on trips, walking around, messing with things, playing poker with the kids, using the bathroom and napping on the couch during that hour. But then it was back to being the back of a head up at the front of the bus while everyone else has fun.

I considered that 2000 Allison series. Not sure how my mechanical bus would work with it. I really want a good auto with a lock-up. I would be happy enough if my wife will get some experience under controlled conditions.

Of course my dad pretended for 40 years not to know how to use the washing machine and my mom always did his clothes...


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