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Old 03-22-2023, 11:23 PM   #1
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Downhill Disco: Tranny Swap, Exhaust Brake, or Retarder

Hello y'all,

I have done a bit of searching on here and I have not exactly found what I am looking for. If I missed this exact convo in the archives please scold me and point me towards it but let me give a quick background.

I'm searching for a bus. What I want is a mechanically injected engine, 30ft body, flat nose. I want to use the bus to be my home near my hobbies. My hobbies are primarily skiing and rafting. Two things that are impossible without mountains. So, therefore I will need to be going up and, more relative to this thread, GOING DOWN.

My problem is that the absolute most common transmission is the AT545 on these model years. I am not sure a 5.9L 12v or DT466 30ft bus were ever made with another transmission. I hope I am wrong.

Now I know that there are some AT545 believers in here. And I know that the lockup does engage in 1st gear. And I know that I could get down most mountain passes safely just with enough time. But with the frequency I plan to drive on these stretches, and the magnitude of the grades in the west (especially the crazy Canucks with 13% grades in places), and the fact that this will be my whole home, I want to be better prepared.

So I reckon that there are three main options if I must pull the trigger on a AT545 (please correct me if there are more).


-Swapping out the tranny for one that locks.

-Swapping out the tranny for one that locks and installing an exhaust brake.

-Installing a drive line retarder.


What I would like to discuss is the pros and cons of each of these. If you are someone who has installed one of these setups how has it performed going down hills? how has it performed in general? would you do it again? how much did it cost?

I greatly appreciate any input, even if its to tell me that I got something wrong. I just want to be able to take my house cool places and feel comfortable and safe.

Cheers,
Zz

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Old 03-23-2023, 06:23 AM   #2
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A drive line retarder on a 545 is an interesting idea. The 545 gets a bad rap because it gets misused or people expect it to work like a “modern” transmission. If you treat it right and know what to expect it can perform very well.
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Old 03-23-2023, 07:01 AM   #3
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the 545 gets a bad rap because its not a highway transmission and people use it like it is.. its a wonderful stop N go transmission.. allison's Highway series transmissions were the MT's (MT-40, MT-64x, MT-65x) for medium duty and the HT-7xx series for the heavier duty (big coaches) stuff.. when people say the 545 is good or bad its like saying a 9/16 stubby wrench sucks because it cant get an exhaust manifold bolt loose.. where as a 16" long flex ratchet is better.. but you can still get that bolt off wit hthe stubby wrench if you pry and pull and beat etc... its simply the wrong tool for the job.. that stubby wrench works great in a tight spot getting a fuel line banjo bolt loose...


Lock up in stop N slow go can actually be a wear item as its constantly on / off.. (sometimes the TCMs were programmed not to lock up until 4th gear on the 2000) hence the 545 is a great school bus route unit in flat cities (like a lot of US cities) running around the neighborhood..



there are plenty of options for tranny swaps to a 12 valve.. and lots of parts to do it.. allison 1000 / 2000 swap kits / parts are sold by many... CAC (custm automatic conversions) and jason@transmissiontuner.com are a couple that I and others have dealt with for swap parts..


I have not seen to many International DT series FE flat-nose busses that were shorties.. they wouldve been sold under the Amtran / ward name in the mechanical DT years.. most mechanical DT466s with autos were MT-643 Lockup non Overdrive transmissions.. 545's started ot sneak in later on low-spec models.. most all the IH transits I saw were full length 35-40 footers



bluebird and thomas both built shorty FE busses with Cummins 5.9s.. I know ive seen one or two that had an MD3060 WTEC-II ... but the vast majority were 545's..





the world-series highway series essentially the modern Day B series and 3000 series came into play in the mid 90s as the first electronic units..



the 545 never locks up in any gear not even first.. there is no lockup clutch in a 545 torque converter nor the valve body fluid circuits to run one..





ive done 2 trans swaps.. one was from a 545 to a Built-up allison 1000 on a navistar T-444E engine and also did a 545 to MT-643 on my mechanicall DT360 bus.. I wanted to keep my mechanical bus all mechanical rather than add electronics into its drivetrain.. thus why not a 1000 on the 360..


both busses were an extremely vast improvement over the 545s.. while i do alot of daily-driving in my busses.. I also run a lot of highway miles as well . in both of my cases my 545s roasted and thats why I swapped them out.. one gave me warning.. the other one just went kaput (luckily 3 miles from home base)... and my 3rd bus still has its original AT540 and will keep it for nostalgia reasons..


if I were in your shoes id buy the bus with the engine you want.. get air brakes and the highest GVWR you can find (bigger GVWR generally means bigger brakes)..



lower rear gearing and a 6 speed double OD allison swap gives the ability to have pretty good engine braking in your lower gears and still a nice RPM range on the highway....


depending on the TCM you use.. (im all about 4th gemn 6 speed).. you can set up "tap-shift" so you can pretty much choose the maximum gear your transmission will use on the down (and up) hills.. the T-handle gives you some control but not as precise..
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Old 03-23-2023, 08:44 AM   #4
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If you're going to be in the mountains that frequently, why not do all 3? Or I guess I should say 2 and 3. Most that have a retarder installed, either telma or hydraulic, are happy with how they work. They're not cheap though, and the problem with driveline retarders is that they create a lot of heat, especially hydraulic units. Exhaust brakes typically don't have that issue, but IMO they provide the least amount of brake force of any device. Maybe it'd be sufficient, maybe not.

But, without a bus, this is all speculation anyways. FWIW a 6bt was rarely found with anything but an at545. It was the base engine/trans package for certain models. A dt466 could be had with an mt643, as the higher HP models wouldn't have been compatible with an at545. But those models aren't all that common either, as most districts didn't opt for the premium options. You could also get a dt466 with an md3060 trans, as those also had a retarder as an option.

I usually recommend people buy a bus with their required options, but I don't think what you want will be readily available, as most buses with high hp and good transmissions will be 40 foot in length as well in order to maximize capacity. I truthfully think you're going to have to buy a bus with the engine you want, and then modify the driveline to suit your needs, as you might never find something that checks all your boxes.

So go with a dt466 and md3060, those are common enough that one shouldn't be hard to find for sale.
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Old 03-23-2023, 09:07 AM   #5
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After owning a truck with an exhaust brake.... don't waste your time. In a 3/4 ton truck they help but in something that is over 10000 pounds no. Go for a retarder. I have one in my rig and it works great.
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Old 03-23-2023, 09:35 AM   #6
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I have seen quite a few TC2000 around Oregon and Washington that meet your specs. 30ft, High Roof, 12v cummins, and MD3060. Many have on-spot chains as well. Alternatively, i have a 24v cummins with a 3060 in a 28ft TC2000. By 2002, at545 was almost out of stock, so most buses had 2000 series or 3000 series transmissions. The 24v can be converted to fully mechanical p-pump and give you more options to work with.



The lockup going down a large grade with the 3060 is pretty nice. You can also get a 3060r that has a transmission retarder.
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Old 03-23-2023, 11:36 AM   #7
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I agree with Booyah. Get the bus with the specs you want, within reason. If downhill is #1 priority, would a dog nose bus work for you?

You live in Colorado, where the good mountain busses come from. In the last couple of years Iíve seen several van front busses(with 7.3) auctioned in Colorado Springs and a dog nose with retarder in (I want to say) Grand Junction.

It might be worth stopping in on a small school districtís maintenance facility on a Friday afternoon next rafting trip. Those guys know when busses are coming up for sale, and more.

Dave
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Old 03-23-2023, 02:13 PM   #8
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You live in Colorado, where the good mountain busses come from. In the last couple of years Iíve seen several van front busses(with 7.3) auctioned in Colorado Springs and a dog nose with retarder in (I want to say) Grand Junction.
The only bus I've ever PERSONALLY seen in person with a retarder was in Estes Park.

I want one, one day. I live in Oregon. Less than 50 miles from the Siskiyou Summit, highest point on I-5.
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Old 03-23-2023, 09:01 PM   #9
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The only bus I've ever PERSONALLY seen in person with a retarder was in Estes Park.

I want one, one day. I live in Oregon. Less than 50 miles from the Siskiyou Summit, highest point on I-5.
All the mountain area buses in CO have retarders.
Last I checked there was a company in CO that specialized in fitting retarders to medium and heavy duty rigs.
If I were in the Rockies with a 545 I'd really want a driveline retarder or lockup at the least.
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Old 03-23-2023, 09:02 PM   #10
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I agree with Booyah. Get the bus with the specs you want, within reason. If downhill is #1 priority, would a dog nose bus work for you?

You live in Colorado, where the good mountain busses come from. In the last couple of years Iíve seen several van front busses(with 7.3) auctioned in Colorado Springs and a dog nose with retarder in (I want to say) Grand Junction.

It might be worth stopping in on a small school districtís maintenance facility on a Friday afternoon next rafting trip. Those guys know when busses are coming up for sale, and more.

Dave
What about a "dognose" makes if less or more capable in mountains?
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Old 03-23-2023, 10:39 PM   #11
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What about a "dognose" makes if less or more capable in mountains?
I racking my brain for the physics of this, maybe more weight on the front brakes? But a loaded rig I don't think is going to make a difference. I drive a water tender up and down stuff that would make most people wince, and the only issues I have are when I'm empty coming down. But that isn't ever going to be an issue with a finished bus.
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Old 03-24-2023, 07:04 AM   #12
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What about a "dognose" makes if less or more capable in mountains?

Sorry. I made a leap in logic and didnít explain myself. The OP listed flat front bus as a priority. I have not seen school districts using FEs anywhere in Colorado. I was simply asking if he preferred form or function in his bus.

In WY I only saw brand new BlueBird FEís 40í long. Kinda like Las Vegas where busses are mostly 40í low ceiling Thomas HDXís.

Dave
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Old 03-24-2023, 07:15 AM   #13
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The most weight on the front axle would be an FE transit, followed by FE conventionals, followed by RE transits.

On an FE transit skoolies should watch their design and conversion, as some of them have lighter front axles which leaves them with little weight to spare for water, batteries, or extra fuel.

Now they're not near as borderline as some of the SRW steel bodied van chassis, but it's still something to consider.
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Old 03-24-2023, 07:35 AM   #14
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Sorry. I made a leap in logic and didnít explain myself. The OP listed flat front bus as a priority. I have not seen school districts using FEs anywhere in Colorado. I was simply asking if he preferred form or function in his bus.

In WY I only saw brand new BlueBird FEís 40í long. Kinda like Las Vegas where busses are mostly 40í low ceiling Thomas HDXís.

Dave
Ohhh my bad. Need more coffee in my life!
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Old 03-24-2023, 01:58 PM   #15
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Ohhh my bad. Need more coffee in my life!

yes!!!! MORE COFFEEEEE!!!
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Old 03-24-2023, 02:10 PM   #16
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I had a couple party buses with exhaust brakes on them. Even driving up and down the hills of the Iowa/Illinois Mississippi valley I rarely used them, it was too much of a hassle flipping on and off all the time. I'd definitely go the retarder route...
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Old 03-29-2023, 09:13 AM   #17
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Haha. I like the title Downhill Disco! I know the feeling. Iím a born and raised flatlander. Driving 12 tons at 7% grade for miles downhill can be nerve wracking. Learning how to use my 3060 tranny I feel pretty good. But next time I get an extra $1k together I think Iíll go for an exhaust brake.

Dave
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Old 03-30-2023, 11:52 PM   #18
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Voith retarder.
Standard on utility vehicles and busses around the hilly Frisco area in California.

https://youtu.be/bXai8z99lUg
.
Vehicles in the auction we attended had some retarders mounted to the differential.
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