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Old 11-22-2016, 01:03 AM   #1
Mini-Skoolie
 
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Found a bus but top speed is 45mph

After countless hours of searching, over many months, I found a bus that is perfect in every way except one. It's top speed is 45mph since it is geared very low. I need it to be 65mph. I'm told it has an Eaton rear axle. The seller made light of this problem saying it is a very common rear axle and conversion parts would be easy to obtain. I did some research and most advice was to avoid used parts since they would have a wear pattern. What are my options in converting the axle ratio and the cost? The sites I looked at were mentioning it could be $2000-$3000 in parts and labor - which is almost what the entire bus is priced at.
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Old 11-22-2016, 01:37 AM   #2
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You'd be better off passing on that one and finding one with the appropriate gearing for your intended use.
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Old 11-22-2016, 01:52 AM   #3
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We had one of our church buses re-geared since it too had a top speed of about 47 MPH.

We had a local shop put in a different gear set for a better top speed. The shop was able to find a good take out that would fit. Total cost was about $2K. But that was about ten years ago.

Before you start spending the $$$ to re-gear, make sure you have enough HP and torque to get you going faster.

When my M-I-L died very unexpectedly I purchased a 12-row IHC/Thomas with the T444/Allison AT540 to move treasures that couldn't or wouldn't be given away or sold back to WA state. It will go 65 MPH. But it needs to be drafting to do so.

Going west across NE whenever I got passed by a semi- if I could draft behind them I could gain almost 5 MPH. But at the first little upgrade, like going over an overpass, I would slow down enough that I would fall out of the draft. At that point I was back to 60 MPH.

Changing the gearing to a highway gearing that is too small numerically could actually make you use more fuel and degrade your performance on any sort of hill.

Almost all of the older buses, older being defined as pre-1995, did not have OD gears. As a consequence most topped out at about 55 MPH. And many topped out at 47 MPH--I owned an 11-row Loadstar/Blue Bird with a 6.9L that would only go 47 MPH. But since they were geared to top out at such low speeds they also had much lower HP rated engines. Back in the '60's 190 HP was considered high HP for a school bus. Even in the early '90's most DT466 and Cummins 5.9L were 190-210 HP. Those kinds of HP spe'c's really can't push/pull a 35' long brick very quickly down the road.

I suppose what I am saying is don't spend the $$$ to make changes if your engine isn't up to the task of going faster. The Cummins 5.9L and IHC T444(E) have a lot of aftermarket support to make them do a lot more thanks to the engines being put into Dodge and Ford light trucks. The problem of taking advantage of most of those go fast upgrades is you will then have to upgrade the cooling system to handle the extra heat. You will also most likely have to start looking at some sort of intercooler or you will melt down your engine on a good pull up a hill.

What started out as a simple re-gearing that cost about $2K could easily end up costing close to $5K or more in order to take advantage of the faster gearing. It becomes obvious very quickly that finding a bus with the power package you want at the beginning can save you a LOT if you have to start changing stuff to make it like you want.
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Old 11-22-2016, 08:26 AM   #4
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cowlitz is right, itsm ore than just the gears... Gears will lower your RPM and REDUCE the torque going to the road...

your mechanical engines have a lot more capability of being increased in power than your elecronic ones...

your DT-360/466 mechanicals you can add about 25 HP just by turning out the fuel screws on the pumps... and that doesnt typically hurt a solid engine...

your cummins have the nost aftermarket support as their variants are similar in busses and in the consumer pickups some of the parts cross.. and those old 5.9 cummins are often swapped out of busses ito people's tractor pull units and sometimes pickups so there is a lot of Love for them on various forums for adding power..

your T-444E is SIMILAR to the Ford Powerstroke 7.3 that was used from 1994-2003.. HOWEVER.. only the PRE-1997 units will have any aftermarket support... in 1997 emissions changed for consumer vehicles but not commercial.. so IHC and ford began using different computers on the T-444E.. at that point theres not much Love for altering or tuning the computer on the T-444E.. a dealer or a good Hacker CAN re-rate a later model T-444E for its top FACTORY horsepower by changing the computer.. most of the school busses ran the T-444E at 170 or 190 HP.. and it can do 210 / 215 with just a computer change.. a dealer can make this change but often will not as the checklist of alterations needed to the bus may include suspension, transmission, etc.. as they have to play cover-their-ass to perform a HP upgrade.. it *IS* possible to hack the computer and force tune to some extent but its not easy..

mechanically the T-444E and the powerstroke 7.3 are essentally similar.. but you need that computer to really take advantage of any mechanical upgrades...

the more i learn about the HEUI system the more i realize just how simple it is... However the real engineering is in getting to know the injector pulse-width relationship to the HPOP pressures and to learn how to precisely control the fuel shots.. the IDM's are easy to drive via an outside source... the ICP / IPR is also easy to read / drive.. so a tech-savvy guy could probably build a computer to run a HEUI engine... esp a non-emissions one like a T-444E / DT-466E

-Christopher
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Old 11-22-2016, 10:08 AM   #5
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When i see people paying $2 k for regearing it makes me wonder if buying a complete rolling differential and just swapping them out would be cheaper. Buy new u bolts and cut the others off.
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Old 11-22-2016, 10:45 AM   #6
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Originally Posted by Versatile View Post
When i see people paying $2 k for regearing it makes me wonder if buying a complete rolling differential and just swapping them out would be cheaper. Buy new u bolts and cut the others off.
it probably is if you have the tools to swap a complete rolling assembly.. im guessing alot of people and shops may not have the tooling to do that whereas swapping gears is much more feasible with more average mechanics tools and jacks to R and R the third member and make the gear changes...

you need some really heavy gear to remove, transport, and reinstall a rolling assembly..

-Christopher
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Old 11-22-2016, 11:39 AM   #7
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My '46 was geared to about 45mph with a 6.17 axle that had originally been paired with a little 90 horse straight six. A 350 Chevy was in it when I got it but the speed was about the same. After replacing the 350 with a little Cummins 4BT I yanked the rear axle and replaced it with a Dana 80 dually geared to 4.30. The original six only had 174 pounds of torque where a box stock 350 is good for about 300 pounds. More than adequate to pull more mph out of the 4.30 gearing. The Cummins 4 banger actually produces a little more than the 350. At 335 pounds, when paired with the close ratio Allison I have in it, it should easily run 63 mph at 1800 rpm. Steep hills will no doubt require some down shifting, but that is to be expected.

I replaced the whole rear axle and re-geared it to the 4:30 for a total of about two grand. Also got disc brakes (now on all 4 wheels) and the ability to run tubeless tires in the process.

Any re-gearing thoughts need to begin with thorough calculations that take gearing, trans, torque and tire size into account as they will all affect how the finished package will perform.

Best of luck...just run some numbers first.
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Old 11-22-2016, 12:21 PM   #8
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This bus is a 1990 Chevrolet (23 ft long, 22.5 in tires) with an 8.2 Detroit Diesel motor and auto transmission. I would have thought an engine of that size could pull a small bus more than 45mph but I'm no expert on buses or gearing. The problem with buying a bus with appropriate gearing is it's never disclosed in the advert, and often the seller has no idea, and it's not stated on the data plate. I only found out with this bus because I specifically asked. There was no mention of top speed in the ad.
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Old 11-22-2016, 12:36 PM   #9
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That is plenty of motor for that bus and more than in most that size. If everything else is "perfect", as long as the price allows, I would not hesitate to do an axle or gear swap. The current 45 mph limit should be a pretty good bargaining point.

BTW...I did the axle swap on mine myself with one helper and hand tools. Some wheel dollies help manage moving the weight (800 pounds?) around.
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Old 11-22-2016, 01:56 PM   #10
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Swapping the third member is much easier and cheaper, you just have to know exactly which rear axle you have
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Old 11-22-2016, 02:03 PM   #11
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Getting all the tolerances dialed in is tricky to do right and more complicated than I would take on personally.
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Old 11-22-2016, 03:54 PM   #12
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Getting all the tolerances dialed in is tricky to do right and more complicated than I would take on personally.
Swapping out a center section/pig ass'y (carrier, ring and pinion, bearings, etc.) from one axle assembly to another is way easier than trying to properly change just the ring and pinion.

And in some cases it might be easier to swap out the entire axle ass'y.
Some junkyards will take your axle assembly in trade towards the one you want.
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Old 11-22-2016, 06:46 PM   #13
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there are no tolerances to set when swapping a third member,
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Old 11-23-2016, 01:10 AM   #14
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Sorry, I'm no mechanic. What is a 'third member'? There are several places where I live (Phoenix AZ) that specialize in axles and differentials. What do think a place like that would charge to swap this 'third member' and would new parts likely be available for a 1990 bus? The rear axle is an Eaton.
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Old 11-23-2016, 06:52 AM   #15
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Originally Posted by Gazolba View Post
This bus is a 1990 Chevrolet (23 ft long, 22.5 in tires) with an 8.2 Detroit Diesel motor and auto transmission. I would have thought an engine of that size could pull a small bus more than 45mph but I'm no expert on buses or gearing. The problem with buying a bus with appropriate gearing is it's never disclosed in the advert, and often the seller has no idea, and it's not stated on the data plate. I only found out with this bus because I specifically asked. There was no mention of top speed in the ad.
Run. Dont walk, run from that bus.
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Old 11-23-2016, 07:00 AM   #16
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Sorry, I'm no mechanic. What is a 'third member'? There are several places where I live (Phoenix AZ) that specialize in axles and differentials. What do think a place like that would charge to swap this 'third member' and would new parts likely be available for a 1990 bus? The rear axle is an Eaton.
"Third member" is the entire gear head or drop in as it is also referred to. If you look at the axle where the drive shaft hooks up, you can see a circle of bolts that hold a large cast part that holds all the gears to the axle housing. If you drained the oil, pulled the axle shafts out each end, which is that small ring of bolts inside the wheels, and took out that large circle of bolts and nuts where the gears are, that entire gear assembly would come out and can be replaced with one with different gears already in it and set up.

But that gear head or third member, is quite heavy and can crush a person. So one needs to have a knowledge of how to support that heavy part before taking on the project.
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Old 11-23-2016, 10:21 AM   #17
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Originally Posted by cadillackid View Post
it probably is if you have the tools to swap a complete rolling assembly.. im guessing alot of people and shops may not have the tooling to do that whereas swapping gears is much more feasible with more average mechanics tools and jacks to R and R the third member and make the gear changes...

you need some really heavy gear to remove, transport, and reinstall a rolling assembly..

-Christopher
Just use the right equipment.One orTwo Good sized lawn tractors or even just a pickup truck and chains. This can be done on dry level ground or a gravel driveway. Changing them gears is something requiring a very experienced mechanic on rear ends. You need a concrete floor to roll that thing around and i think they have a special jack to lift them up. The same shop could do it for you; so a guy wouldn't have to do it himself. I would guess it should be cheaper to have done. I think it would be quite the up grade to a bus to buy the complete diff/tires etc. Get it home and clean it up and IRAN (inspect and repair as necessary) add in a new pair of rear shocks . Do everything you can too it so as you won't have to buy any shop extras. You deliver it and they roll it under hook it up and then you pay them for swapping your excellent tires over. You might get a new set of tires on the rear end you buy. So many feel just over whelmed due to the size of the toys. Don't be. Leverage is your friend when dealing with this big stuff.
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Old 11-23-2016, 06:18 PM   #18
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Yes, I know this is a Ford 9in rear axle, but the picture is good for showing what the third member is. If you look at the picture, the Orange part is the "Third Member"
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Old 11-23-2016, 10:55 PM   #19
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Changing out third members is not hard, just like said before. Big and heavy, probably close to 200 pounds. Getting it out is easy, piece of 4" stryofoam under axle housing. Pull axles, unbolt third, hammer and pry gently on flange till it falls out on foam. The hard part is getting it back in, gravity is the big obstacle on this part. I cut the head off of couple bolts and loosely screwed them back into housing as a guide. After a couple other bolts started I took out guide bolts and ran the rest of the third member bolts in. Here is a quick pic of my third member swap.

20140625_111923 by Hvbuzz, on Flickr



Quote:
Originally Posted by Deezl Smoke View Post
Run. Dont walk, run from that bus.
I can't agree more with Deezl. An 8.2 is fine while working properly, once there is a problem its a boat anchor. Just google Detroit Diesel 8.2 and find me 2 people that tell you not to run. The hundreds of others will tell you how bad it is to repair.

So I would keep looking for a better option.
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Old 11-24-2016, 08:05 AM   #20
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Originally Posted by Hvbuzz View Post
Changing out third members is not hard, just like said before. Big and heavy, probably close to 200 pounds. Getting it out is easy, piece of 4" stryofoam under axle housing. Pull axles, unbolt third, hammer and pry gently on flange till it falls out on foam. The hard part is getting it back in, gravity is the big obstacle on this part. I cut the head off of couple bolts and loosely screwed them back into housing as a guide. After a couple other bolts started I took out guide bolts and ran the rest of the third member bolts in. Here is a quick pic of my third member swap.

20140625_111923 by Hvbuzz, on Flickr





I can't agree more with Deezl. An 8.2 is fine while working properly, once there is a problem its a boat anchor. Just google Detroit Diesel 8.2 and find me 2 people that tell you not to run. The hundreds of others will tell you how bad it is to repair.

So I would keep looking for a better option.
Great advice, and with a picture no less. Line up pins are one's best friend.
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