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Old 12-06-2021, 01:39 PM   #1
Mini-Skoolie
 
Join Date: Oct 2021
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Skoolie Gearing

Hey all,

I ran into an interesting situation . I am exploring different ways to increase speed and fuel economy on my bus. It is a 1995 International 3800 30ft bus with DT466 engine and MD 3060 Allison transmission. I just found out my gear ratio is 6.14. Has anyone ever had a bus geared this low? Anyone ever change the ratio and get better speed/mpg?

Also looking for advice for unlocking a 6th gear. A few places have told me my transmission does not have 6 gears, it has 4 with 5 as an overdrive. Finally, with this combination of hardware, is it safe to increase my governed speed without upgrading the drivetrain and transmission? Thanks in advance!

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Old 12-06-2021, 01:56 PM   #2
Bus Geek
 
Join Date: May 2009
Location: Columbus Ohio
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Year: 1991
Coachwork: Carpenter
Chassis: International 3800
Engine: DTA360 / MT643
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dont turn the RPM governer on the engine up! you can if you want to rebuild your engine sooner.. the DT466 is a pretty long stroke engine and piston speed becomes an issue.. not to mention dismal fuel economy running it flat out at 2600 let alone any higher..



unlock 6th gear and regear the rear down in the mid 5s is what id do..



if you cant find anyone to unlock your WTEC-II TCM's 6th gear then id plan on a regear down to 5.13 or 5.39 at most..
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Old 12-06-2021, 01:57 PM   #3
Bus Nut
 
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Quote:
Originally Posted by JSquire7 View Post
Hey all,

I ran into an interesting situation . I am exploring different ways to increase speed and fuel economy on my bus. It is a 1995 International 3800 30ft bus with DT466 engine and MD 3060 Allison transmission. I just found out my gear ratio is 6.14. Has anyone ever had a bus geared this low? Anyone ever change the ratio and get better speed/mpg?

Also looking for advice for unlocking a 6th gear. A few places have told me my transmission does not have 6 gears, it has 4 with 5 as an overdrive. Finally, with this combination of hardware, is it safe to increase my governed speed without upgrading the drivetrain and transmission? Thanks in advance!

I'm not sure you have an MD3060, I don't think they made that transmission in 1995? Might want to get a picture of the gear shift and hopefully the ID tag on the transmission if possible.
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Old 12-06-2021, 02:23 PM   #4
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I had a ham friend that had a 94 motorhome with the 3060 that died back in 09 the tcm crapped out. It had all 6 speeds forward and then had 1. Tow bill and part was just south of 2000 dollars. I drove it once before he traded it in and that transmission was really refined compared to the older mt/ht series. That convinced him to trade it in on a new one. He used it twice and passed away.
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Old 12-06-2021, 04:02 PM   #5
Skoolie
 
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I was about to come on here an post the same kind of question as this one... I just got a 28-foot bus with an AT545 and it caps out at 50mph. I talked to a transmission shop and they feel the re-gearing alone is enough to get it up to 60 or 65. They are looking at this being a $3000-$5000 job for parts and labor.



How big of a job is this? I'm curious if a shop does it what kind of price range should I be looking at?
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Old 12-06-2021, 04:06 PM   #6
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if you are mechanically inclined and have the tools and jacks then it is only a few hours job and you can get used center sections with the gears you want and just change the center section.
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Old 12-06-2021, 05:09 PM   #7
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Determine what rear axle you have and the ratio, then call a few truck wrecking yards. Re ratio about .8 and you will be about right. If you have a 5.89 multiply by .8 and that would be 4.70. Then add a large transmission oil cooler or you will over heat your transmission. Do not over gear a 545 or you will be un happy.
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Old 12-06-2021, 05:26 PM   #8
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rear gears

I bought a used rear differential for my bus project... going from 4.88 to 3.73

the differential shipped to the work shop door $800, that was two years ago.

I had to have a forklift at the address. no residential deliveries.

I had to make sure the that the yoke of the differential was the same ujoint as the one I had. I had to make sure the splines on the axles were the same as the ones in my rear end. It was possible, in my case to buy a differential for the correct axle housing but not fit my axles or ujoint.


needed gear oil, hand tools couple of gaskets for axle flanges, sealant in a tube for differential,

wheels stayed on the ground, removed driveshaft. removed both axles. drained gear oil out of axle housing. removed bolts for differential. I welded a plate to the floor jack I was using to "catch" the old diff coming out. used prybars to dislodge it.

removed speed sensor from diff. removed diff from floor jack. I used an engine hoist for this.. I already owned one. used hoist to put new diff on jack. used bits of 2x4 to prop replacement diff up so that I could pretty much "plug" it in place. used a ratchet strap over the ujoint flange to hold it in place. Ithreaded two long bolts with the heads cut off into the axle to be alignment pints...... I cut a slot in the ends so I could use a slot screw driver to take them out.... clean, scraped and degreased mounting flanges on axle and differential... I use a grey permatex sealant that seems to be very much like the grey sealant used on toyota. just a fine bead about 1/8" - 3mm in diameter. moved the diff inplace far enough to engage those two pins. slid the assembly backwards so that I could get the bolts all started by hand. I cleaned all the bolts too. use a thread chasing tap and die on all threads and inspect all threads, hand thread in all bolts before doing any of this. Made sure all bolts were in good condition before getting the heavy diff in the way.

tighened all bolts just tight enough to squish sealant. removed pins and install bolts there.
I tested the axles in the side gears when the diff was not under the bus.. each axle. check bolt torques on random bolts of the differential before getting the diff off the pallet.

If you have leaky wheel hub seals, now is the time to think about doing those. 'cause you have to have axles out to do those anyways....

all day long job. I built the jack pan the day before, gathered together the 2x4 to make a diff holder. those alignment pins, all the prep stuff was a full day before the swap day. Start to finish was two full 8 hour days. one day of prep work and one day of work. another three hours the third day putting away all the tools I had out.

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Old 12-06-2021, 05:32 PM   #9
Skoolie
 
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Engine: DT
Thanks for that input and advice!



Outside of the 50 MPH limit, the bus drove great from Alabama to Connecticut. For a 33-year old, but I was quite impressed! If I can hit 60 mph with it, I think it would be the perfect bus!
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Old 12-06-2021, 05:44 PM   #10
Bus Geek
 
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Chassis: International 3800
Engine: DTA360 / MT643
Rated Cap: 7 Row Handicap
I installed my own rear diff in my superior.. it was heavy but i had a couple grand in a completely Reman unit built to my spec .. that includes fluid and other parts.. I had my driveshaft U-joints replaced and the set balanced / phased also at the same time.. dont even have to take the wheels off to change the 3rd member on most all of these busses..
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Old 12-07-2021, 11:23 AM   #11
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Quote:
Originally Posted by s2mikon View Post
Determine what rear axle you have and the ratio, then call a few truck wrecking yards. Re ratio about .8 and you will be about right. If you have a 5.89 multiply by .8 and that would be 4.70. Then add a large transmission oil cooler or you will over heat your transmission. Do not over gear a 545 or you will be un happy.
Depends on the setup. My "overgeared" 5 window with a Cat is HAPPY af with a 3.42 in the rear and the 545 stays nice and cool.
I wouldn't do that with a split radiator or a heavy bus. But keeping the engine in its torque curve all the time makes my bus super happy and a great driver.
On a heavier buses 3.42 would be way too high. But decent gearing and a trans cooler/Transynd fluid change is a nice way to go for any regular 545 skoolie application. In a full size bus with 545 I'd go 4.44 or 4.10 depending on the setup.
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Old 12-07-2021, 11:25 AM   #12
Skoolie
 
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Chassis: CE300
Engine: DT
Mine is a 28 foot with a Ford V6 diesel in it (198.
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Old 12-07-2021, 11:33 AM   #13
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Mine is a 28 foot with a Ford V6 diesel in it (198.
A straight six? I've not seen a v6 ford diesel in a bus.
My 22 footer likes its highway gearing. I've got a straight six, 190hp cat.
With a ford/new holland and a few extra feet of bus you probably want to gear it a bit lower than what I have.
What size are the tires?
You can definitely get 60 out of it.
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Old 12-07-2021, 12:02 PM   #14
Skoolie
 
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Engine: DT
I'm going off of the VIN lookup on the AutoZone website which returns:


"1988 Ford B600 6 Cylinders P 6.6L Turbo Diesel 401 CID"


Tires are 9R22.5
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Old 12-07-2021, 12:05 PM   #15
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Check your rim size for width. You may be able to go to 10r 22,5. I think you have 6 hole wheels.
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Old 12-07-2021, 12:21 PM   #16
Bus Geek
 
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Quote:
Originally Posted by cofrari View Post
I'm going off of the VIN lookup on the AutoZone website which returns:


"1988 Ford B600 6 Cylinders P 6.6L Turbo Diesel 401 CID"


Tires are 9R22.5
Ok yeah that's an inline six.

What rpm is the engine at when you're doing 50mph?
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Old 12-07-2021, 12:25 PM   #17
Skoolie
 
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Engine: DT
Unfortunately there is no tach on it. I just ordered one off of AutoHack, so hopefully I can install that easily enough.


I kind of went by sound to ensure I never let the engine get as loud as it did right before it shifted.
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Old 12-07-2021, 12:27 PM   #18
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Quote:
Originally Posted by cofrari View Post
Unfortunately there is no tach on it. I just ordered one off of AutoHack, so hopefully I can install that easily enough.


I kind of went by sound to ensure I never let the engine get as loud as it did right before it shifted.
When you get a tach you can plug your number into this calculator-
https://spicerparts.com/calculators/...rpm-calculator
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Old 12-11-2021, 04:34 PM   #19
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My first bus had a rear differential of 6.14 with the md3060 5th gear and Cummins 5.9. It maxed out at 65 MPH at 2500 rpm. If I had got 6th unlocked on that it would’ve brought the rpm down to 2250 at 65 MPH.
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Old 12-11-2021, 04:52 PM   #20
Skoolie
 
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When I did a air ride conversion I did a axle swap as well. I even swapped the ring and pinion gears in the rear axle myself. ($300 for Rockwell gearset)
There are a lot of companyís in the renamed trans/diff business that will sell you a center diff set up or just a good set of gears
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