Thinking of changing Rear end gear ratios

[Ryannmelis]

I am thinking of changing my rear gear ratio. I have a DT360 with an AT545. Has anyone here changed their ratio? What was the outcome? How much were the parts? I would like to drop my RPM’s down a little. I would love to run 60 at 2500 RPM’s in fourth.

[Brad_SwiftFur]

I have yet to change the gearing in my bus, but having checked into it, I can get it done for about $800 or so; this is with me pulling and reinstalling the axle module. The module will be refurbished, new bearings, seal, etc.

[EastCoastCB]

Originally Posted by Brad_SwiftFur

I have yet to change the gearing in my bus, but having checked into it, I can get it done for about $800 or so; this is with me pulling and reinstalling the axle module. The module will be refurbished, new bearings, seal, etc.

Its a good upgrade for the money, if you ask me.

[Ryannmelis]

Well that sounds good. I will be looking at around $400 to do it on my own. Not bad.

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[Brad_SwiftFur]

Originally Posted by Ryannmelis

Well that sounds good. I will be looking at around $400 to do it on my own. Not bad.

If you are skilled and knowledgeable on how to remove, reinstall, and properly adjust the ring & pinion then that's not bad. However, since I am not, then spending the extra to have the gearset professionally installed & adjusted makes sense to me - plus they give a warranty.

Or is that for a used module from a boneyard?

[Brad_SwiftFur]

Speaking of gear swaps, anyone have a suggestion as to what gear ratio I should consider? Running gear as follows:

IH 9 liter engine
Allison trans (I am thinking it's a 545)
Hydraulic brakes

Current gearing 5.38:1, top end around 50-55, would like a top end around 70 but not if it will overwhelm the engine. Thinking maybe around a 4:10 ratio?

[onenationundergoat]

We started with 6.14 and changed it out for 4.7 in our DT350 with AT545. Original speed at 2700rpm was 47mph, 52 downhill. With the other gears our new average is about 59 and we've gotten to 70 once downhill but it was scary and about 3200rpm before we noticed. I bought the 4.7 hog head from Kubla on here. He was switching his out for 4.1. I paid him $350 and did the install myself. Not hard at all if you have the whole thing. Eventually I'd like to get 4.1 and switch the tranny too.

[Brad_SwiftFur]

70+ in a bus won't bother me, as I am accustomed to driving large vehicles, and I worked for a hatchery some time ago. They ran purpose-built buses (mostly extra headroom, windows with panels instead of glass, and lots of ventilation) to haul freshly hatched chicks, and they were geared for 70+.

[Jolly Roger]

I have an 8.2 with 545 and 6.5 gears.
I want to do a gear change real bad but my rear end from what I can find has been out of production for awhile and I can't find gears for it.
Everything suggested to get me to 55-65 range was in the 5 and high fours before I started burning up the 545.
But you also lose any hill climbing power or so I am told.
Another option I have is going to taller tires which are supposed to help but once again I am not finding my Dayton split ring not rim. Currently I have 9r20 tubed rims and when I can find them I can go to 10r22.5 tires which should pick up some speed but the bus will bounce/dance around more because of the taller tires.
I wanted a garage to do mine because of warranty but the cheapest I have found is 3000$ if I buy the gears and bring them the hog head??
If I have to do all of that in a gravel driveway and all of the neighbors kids running around daily (6-10) I can change the gears myself. I just wanted the warranty from a shop so I didn't have to worry about setting the spacing,lashing,backlash and I am on the side of the road somewhere 6-months later cause I mucked up.
Brad swift fur
I don't know your engine but I have the same tranny I think?
Is yours a 4-speed if so its the 545 without the lock up torque converter.
Everything I have heard was to leave the motor at its factory settings for longevity.
The 545 has specific temp and speed ratings or your gonna be looking for a tranny next?
With the gears you stated for yours I think your weak point is the tranny not the rear gears.
But that's just my opinion and some research knowledge from my lead sled (49-mph) build
I am just trying to get to 55-60 and your already there.
Wish you luck making 70 maybe we can wave at each other when your passing me.
Good luck

[Dragonpop]

My suggestion would be to leave the rear end alone and change out
the transmission to a 5 or 6 speed model like the Allison 2060 or md3060
which are 6 speed transmissions which are double overdrive which will
give you the lock up converter for mileage and a the low gear starting
power. My bus has an MD3060 but only has 5 speeds open with 6th gear
locked out at present. With 12r22.5 tires it is doing 65mph at 2000rpm.
my differential ratio is 5.38, top speed at 2400 rpm is 85mph.

[Brad_SwiftFur]

Originally Posted by Jolly Roger

I have an 8.2 with 545 and 6.5 gears.
I want to do a gear change real bad but my rear end from what I can find has been out of production for awhile and I can't find gears for it.
Everything suggested to get me to 55-65 range was in the 5 and high fours before I started burning up the 545.

What model of rear axle do you have? I might be open to a deal on my module with 5:38 gears ...

Originally Posted by Jolly Roger

Another option I have is going to taller tires which are supposed to help but once again I am not finding my Dayton split ring not rim. Currently I have 9r20 tubed rims and when I can find them I can go to 10r22.5 tires which should pick up some speed but the bus will bounce/dance around more because of the taller tires.

When you swap the rims, the 22.5's will *NOT* have a ring, they should be a direct, bolt-on replacement. Local junkyard sells these rims for like under $50 each. It'll give you a little more top end, I doubt you'll notice much more "bounce and dance".

Originally Posted by Jolly Roger

I wanted a garage to do mine because of warranty but the cheapest I have found is 3000$ if I buy the gears and bring them the hog head??
If I have to do all of that in a gravel driveway and all of the neighbors kids running around daily (6-10) I can change the gears myself. I just wanted the warranty from a shop so I didn't have to worry about setting the spacing,lashing,backlash and I am on the side of the road somewhere 6-months later cause I mucked up.

My quote was for me removing the module, and the shop doing the actual gear install, spacing, setting, etc. They give a warranty. For the $3000 you are saying, I should hope that is swapping the entire rear end for a rebuilt one ... my usual shop occasionally does these for big rigs, and that's about the going rate for a complete, rebuilt axle swap.

Originally Posted by Jolly Roger

Brad SwiftFur
I don't know your engine but I have the same tranny I think?

It was an engine IH built in the late 70's and up through 1987 to compete with the 3208 Cat motor, a "poor man's diesel" for places that did not want to spend the extra on the DT466. Popular in school buses and many municipal vehicles, it was discontinued at the end of '87 because it could not meet '88 emissions, and was replaced by the 7.3 / DT444

Originally Posted by Jolly Roger

Is yours a 4-speed if so its the 545 without the lock up torque converter.

I think so. VIN pulls up a Spicer trans, but bus was previously owned by a church, so we think it was very likely retrofitted. I need to get a look at the trans ID plate to make sure.

Originally Posted by Jolly Roger

Everything I have heard was to leave the motor at its factory settings for longevity.

I plan to.

Originally Posted by Jolly Roger

The 545 has specific temp and speed ratings or your gonna be looking for a tranny next?
With the gears you stated for yours I think your weak point is the tranny not the rear gears.

That's why I wanted to ask before I committed to doing a gear swap.

Originally Posted by Jolly Roger

But that's just my opinion and some research knowledge from my lead sled (49-mph) build
I am just trying to get to 55-60 and your already there.
Wish you luck making 70 maybe we can wave at each other when your passing me.
Good luck

Let me know what axle you have ....

[Ryannmelis]

My only worry with swapping the transmission is drive shaft length. I just was on the phone earlier with International. The parts guy looked up my rear axle I have a dayna 190 with 5.38 gear ratio. I am going to look for a ring and pinion set for a direct swap. Depending on parts availability is what gear ratio I will end up with. if I can't find the parts. I will have to change my plans. Now that I have the axle information I can see what the gear options were for that axle and find part numbers for the ring and pinion sets. By far the cheapest route is a ring and pinion set with an overhaul kit.

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[Brad_SwiftFur]

If I'm going to consider a trans swap, I'm going to find manual. Somewhere there has to be all the necessary hardware to revert it back to a manual. One with an overdrive would be sweet ... and convert the speedometer to electronic.

[Ryannmelis]

Ring and pinion sets are available. So far I have found 4.11 up to 5.38. has anyone here changed their gear ratios with the 545? I am curious how the transmission acts on hills with a higher geared rear end.

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[onenationundergoat]

Originally Posted by Ryannmelis

Ring and pinion sets are available. So far I have found 4.11 up to 5.38. has anyone here changed their gear ratios with the 545? I am curious how the transmission acts on hills with a higher geared rear end.

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Our 545 gets us up any hill (Rockies and Appalachians many times) with no issues. Underpowered and slow for sure (20mph), but very reliable and no complaining. Unless it's a really big hill I usually only have to go in 3rd (~2000-2200rpm). Rarely in 2nd and almost never in 1st.

[Ryannmelis]

do you have the R D 3 2 1 shifter or another type? how is your mileage?

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[onenationundergoat]

yeah it's automatic RD321. we've never been able to exactly calculate the mileage because out odometer and speedometer are wrong due to the 4.78 gear change, but our best estimate is 10mpg. Been driving it for around 15,000 miles.

[Ryannmelis]

food for thought Thomas.com has all the gear ratios.

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[Jolly Roger]

Brad
I have an eato rear end
Msg model 16s
Model 16121
Head 121523
I haven't found anything to reference these numbers to?
And that price was with me buying the new ring and pinion and bring them the head only?
I thought it was ridiculous but still haven't found the gears and haven't found any rims around here yet.
I did find some on eBay for 60$ a piece but they were in Illinois .
Thanks

[cadillackid]

you are a 9R20 and want to go to a 10R22.5? doesnt that mean the star hub will be the wrong size on the daytons?

I went from 10R22.5 to an 11R22.5 and went from Load range F to load range H which is a tad bit harder ride although ive got air ride rear so that helps..

I went up in load because im now with very standard truck tires.. uniroyals, so very easy to match and replace if I damage one...

im on daytons but they are tubeless and not a split rim..

the big issue with split rims is that very few shops will touch them and no mobile service will that I know of...

dayton rims are still somewhat common on older dump trucks still in service in many areas so shops know how to work on and align daytons, just not split rim.

-Christopher