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Old 08-20-2010, 09:47 PM   #1
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changing gear ratios

is it possible to change gearing?

i figure it would free up a few mph on the highway and maybe drop the rpms?

just curious at this point as i havent purchased yet but ive seen a few folks mention top speeds of 60 with the engine screaming.

is it reasonable to want sub 2,000 rpms but able to cruise at 65+? sounds like it would be easier on the engine and get better mileage.

are some rear axles a better choice to change ratios?

from what ive read, skoolies are designed for low speed around town grunt work...makes sense.
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Old 08-20-2010, 09:48 PM   #2
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Re: changing gear ratios

oh i forgot to ask...

tire diameter comes into the equation...has anyone altered theirs? is it safe?
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Old 08-22-2010, 01:30 AM   #3
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Re: changing gear ratios

Yes its doable. The dealer quoted me $1800 total for parts and labor. Since you are still shopping for a bus, why don't you just limit your search to buses that already have the proper gearing. Some school districts have activity buses that will run 70+, and there fuel mileage is as good, if not better, than many gear-bound buses that can only do 55 to 60mph.
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Old 08-22-2010, 05:07 PM   #4
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Re: changing gear ratios

oh i intend to look for the right gearing...was wondering if it was one of my criteria that i could compromise on purchase and change later if i needed to.

some of the other specs i would like cant be changed. at least not easily.

$1800 doesn't sound too bad, i assume it would be dependent upon the axle type and manufacturer?
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Old 08-22-2010, 10:41 PM   #5
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Re: changing gear ratios

[quote="Cygnusaa"]oh i intend to look for the right gearing...was wondering if it was one of my criteria that i could compromise on purchase and change later if i needed to.
some of the other specs i would like cant be changed. at least not easily.

Once you locate the body and drive train that suits your needs and price range, anything else that doesn't satisfy you can be upgraded. In fact, converting a school bus is a series of upgrades. We're just starting with the most solid and safest of structures. Sorta like building a house, first and foremost a good foundation, and that's where the the school bus chassis really separates the boys from the men and why most of us prefer it as compared to the glitter of the big box tent on wheels, solid structure first.

Changing the rear axle or center section pumpkin, is a minor upgrade as compared to the total cost of a conversion. Tho most of us won't do that, mainly because we're not in that big of a hurry and the payback is long term unless you plan to put some very serious high miles on your skoolie. Most truck repair shops can change your axle ratio at a cost of around 2 grand.
The only catch 22 is, you may or may not see an increase in fuel mileage. A lot depends on how you drive. You will have a quieter motor if you don't increase your speed or weight too much.
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Old 08-23-2010, 01:34 PM   #6
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Re: changing gear ratios

good foundation is where its at...its why im looking for a big yellow tube

is there anything i should steer clear of axle-wise?

are there certain makes that are known to be problematic?

i havent come across too many here with rear axle issues. that tells me most are solid.

if i had to guess on yearly mileage i dont think i could be accurate. i only have a rudimentary idea of the places id like to spend time...i really want to have at least 1 property to call my own so i can do what i want...its a big unexplored country for me...i suppose i would start here on the east coast and make my way west...keep it casual and not be in a hurry...plan ahead to a degree of course but not sure how it will translate into miles...something tells me much less than 12k a year since id have to be judicial with use plus id stay in areas for awhile...

what do the rest of you rack up yearly?
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Old 08-27-2010, 03:12 PM   #7
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Re: changing gear ratios

Try this link:

http://www.csgnetwork.com/rearendgearcalc.html

And Here: http://www.idavette.net/tech/ratioc.htm

Good info. I'm not sure where I got it from, probably somewhere here.
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Old 08-29-2010, 12:15 AM   #8
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Re: changing gear ratios

thanks coma...that will come in handy
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Old 08-30-2010, 03:10 AM   #9
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Re: changing gear ratios

Since we're talking gears here, I just bought a Rockwell 22k lb whole rear axle with everything attached but the tires. It has 3.73 gears plus the wiring for ABS brakes. The brake shoes look to be about 90% new and other than rims, I wil need to buy a yoke b/c this spindle looks larger then the one on my 19k lb R190 axle.

My plan was to just change out the pumpkin, but the price on this new rear end was too good to turn down. I may now have to carry two spare tires b/c my bus came with Dayton wheels and this new one uses Budds. I guess I could change out the front hubs to Budds later, but the IH dealers are very proud of those hubs.

Has anyone actually swapped rear ends on their bus? Other than jacking up the rear end high enough, what other problems has anyone encountered. My bus already has air brakes and air ride but as far as I can tell, no ABS. I'm hoping that not connection the ABS wiring won't cause a problem. Any ideas?

My current rear end has 4.44 gears.
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Old 12-26-2016, 05:30 PM   #10
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Dear Sir,
I do realize this is a very old post.
We would like to know how the gear
change worked out, milage, engine
RPM and difficulty. Thank You very
much.
Sincerely, SCARECROW.
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Old 12-27-2016, 09:49 AM   #11
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I have an 2001 AmTran 84 pax RE 466E 250hp MD3060 with tinted windows that I swapped the rear end in. I think it cost me about $1400-1500. I would have to dig out my folder to see how low I went but it made a HUGE difference cruising the interstate. We took a church group from Northern WV to Orlando FL and the relief driver kept going well over 80mph before he would notice it. He was a retired school bus driver so, he has experience. On that trip we were loaded heavy. I live on the top of a mountain so gearing change did affect the hill climbing, but not by much. I haven't converted the bus yet, but I have pulled all the windows, resealed them, 3 batteries, 200 amp alternator, added more speakers, added power points thru the back of the bus and new driver front kingpin, mid ship heater. I have been wanting to get started on the conversation, but I may sell it if the price is right. I bought the bus in Orlando Fl, it cool taking it back to its home -lol

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Old 03-01-2017, 09:15 AM   #12
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Originally Posted by jctrembly View Post
I have an 2001 AmTran 84 pax RE 466E 250hp MD3060 with tinted windows that I swapped the rear end in. I think it cost me about $1400-1500. I would have to dig out my folder to see how low I went but it made a HUGE difference cruising the interstate. We took a church group from Northern WV to Orlando FL and the relief driver kept going well over 80mph before he would notice it. He was a retired school bus driver so, he has experience. On that trip we were loaded heavy. I live on the top of a mountain so gearing change did affect the hill climbing, but not by much. I haven't converted the bus yet, but I have pulled all the windows, resealed them, 3 batteries, 200 amp alternator, added more speakers, added power points thru the back of the bus and new driver front kingpin, mid ship heater. I have been wanting to get started on the conversation, but I may sell it if the price is right. I bought the bus in Orlando Fl, it cool taking it back to its home -lol
Was just searching for info on changing the gear ratios. So a couple of questions for you...

1) Did YOU change the gear ratio or did you have it done by someone else?

I've not paid a lot of attention while under a bus but swapping out the entire axle can't be that much work with the proper lifting equipment.

2) What was changed; the internal gears, the pumpkin, or the entire axle?
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Old 03-01-2017, 09:26 AM   #13
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1. I don't have the ability to do it myself, wish I did though. It takes a bit of knowledge ensure everything is adjust prior to bolting everything up also.

2. Just the internals.

Your cheapest option is to find a used/ rebuilt rear end, I couldn't locate one so I had to go the new route. The ratio I wanted just isn't common enough for them to be laying around it seems. Right now I don't remember what we went with and my wife 'cough' has misplaced the file folder with all that info... Same folder as the title. No biggie. Lol.

She seems to shuffle stuff around every now and then, it drives me up the wall. So now I let her file everything and ask her to get the paperwork I need. Only this time.... She's forgotten where she put it.

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Old 03-01-2017, 09:27 AM   #14
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Oh, I'm going to convert out bus. The kids are slowly taking out the seats. Once I finish up a few projects I'll help them. In the meantime I don't mind them owning part of the process ;)

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Old 03-01-2017, 09:43 AM   #15
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Originally Posted by jctrembly View Post
1. I don't have the ability to do it myself, wish I did though. It takes a bit of knowledge ensure everything is adjust prior to bolting everything up also.

2. Just the internals.

Your cheapest option is to find a used/ rebuilt rear end, I couldn't locate one so I had to go the new route. The ratio I wanted just isn't common enough for them to be laying around it seems. Right now I don't remember what we went with and my wife 'cough' has misplaced the file folder with all that info... Same folder as the title. No biggie. Lol.

She seems to shuffle stuff around every now and then, it drives me up the wall. So now I let her file everything and ask her to get the paperwork I need. Only this time.... She's forgotten where she put it.
Might I suggest tattoos?

The ex did the same all the time (shuffle). The gf does it more often than the ex and then doesn't even remember where it was shuffled. I've "had words with her" about that. As we aren't cohabiting, it isn't too big a deal (yet). There will be more words if we ever do.

Reading another thread that someone was considering going from 4.78 to 3.73. I haven't played with the calculators but that has to be worthwhile. Looking at an auction now that has one bus with a 4.63 and the rest are 4.78. Another is 5.22 with the AT 545/C7. Much rather have the 8.3/643/3.73.

And there is nothing wrong with slave labor. I fully endorse that!!
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Old 03-01-2017, 09:47 AM   #16
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in my opinionm unless you have the tools, knowledge, and source of Cheap parts you are best to spend the upfront money buying the bus with the drivetrain you want... if you have to buy a bus, buy new parts, or have them pulled from a donor, and have them installed in your bus.. you may be at much more cost than you wouldve been by bidding up a bus by another couple 1000 that has the drivetrain you want..

if you can put it together yourself without hiring a shop and can visit a boneyard to pull your old parts yourself, then I say yeah you can save alot of dough by purchasing the bus with wrong gears and re-gear yourself..

-Christopher
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Old 03-01-2017, 09:49 AM   #17
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I like the tattoo option... She doesn't like pain, perhaps one tattoo and the shuffling will stop. Well, one can hope.

I believe (double check me) a 643 final output in top gear is 1:1. With the MD3060 it's a 6 speed with double overdrive. Those number effect your rear end ratio. It really bugs me that I don't know what mine is. Believe me I've searched for that folder.

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Old 03-01-2017, 09:52 AM   #18
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I search for what I wanted, the only two things I didn't get was full belly storage and the gear ratio I wanted. Well, after looking at how easy it is to work on an Amtan RE I didn't care about the belly storage. The rear end, yup, I coughed up some cash and paid to make it what I want. I fully agree to find what works rather than try to make it work.

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Old 03-01-2017, 01:08 PM   #19
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Me and my dad changed our rear gears ourselves. All you need as a concrete pad, a motorcycle jack, and the entire gear assembly hog head. It's super simple. Took maybe two hours, if that. Slip out the axles, disconnect the drive shaft, take off about 18 bolts, use the motorcycle jack to get the old one out and new one in. Easy peasy.
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Old 03-01-2017, 01:16 PM   #20
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take off about 18 bolts,
It's big, it's heavy, and it's ugly but 18 bolts?!!? I hate it when they do that.
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