At545 swap

[Ghrasshopper]

I have a 1983 Thomas bus with a Detroit diesel 8.2l engine and an AT545 transmission. I think my transmission is giving out and I am entertaining replacing it. My question is if there is a better transmission I can swap it with that would fit with a better engine at some point in the future or if it’s best just to replace it with a used At545 and do both swaps together at a later date. Thanks for the advise in advance.

 

[Johnthebusboy]

Hi, I replaced my AT-545 with a 5 speed spicer.
Works well if you a stick shift. The part is figuring out the clutch linkage.

 

[CHEESE_WAGON]

Depends on what you're able to do and what you ultimately want. If you plan to swap both, I would say it's best to just wait until you can afford to buy a donor vehicle such as a late model box truck with a complete engine / drivetrain that can be easily swapped (7.3 IDI / MT643 for example). There are different bellhousing patterns, and some swaps require adapters that are more easily sourced from a complete setup from a donor vehicle.

If you have the skills or know people that do, you may even consider stretching / shortening a later frame for a body swap (search Dave Kenny 86 Ford 07 Kenworth) that can get you some other nice upgrades if done right (front A/C, ABS, front disc brakes, highway gears). But that means you'll want to park it for the time being. No sense risking a tow bill that can put you back to square one.

 

[cadillackid]

cheese wagon has irt right.. there are different bell housing patterns..



im not an expert on Stck-shift conversions.. personally im an automatic kinda guy.. others can chime on on the difficulty of a stick-conversion.





I dont kinow the 8.2 specifically..

the AT545 is an SAE3 bell housing pattern. (small)

the "easiest" non-electronic transmission candidate as an upgrade would be an MT643


the MT643 has an SAE2 bell housing pattern..(medium size)..


on international, CAT, and other medium duty engines, the engine is actually built as an SAE2 bell housing pattern.. and then an adapter riung is used to make it the smaller SAE3 to hold an AT545.. I have no idea if the 8.2 is built this way or only has an SAE3 housing on your bus..



taking a picture of the bolts on poart of your bell housing would help..



in essence if you see the transmission bell has a ring of bolts and then a seond larger ring of bolts holding it to the engine housing then you have an SAE2 engine thats been adapted to SAE3. if this is the case it opens you up to a wider range of possible transmissions that can be installed.. installing an MT643 will require your engine is an SAE2 adapted down to an SAE3 (2 rings of bolts).. and will likely require different flexplate, hub spacer changes, and possibly a secondary mount. if you have hydraulic brakes wit ha drum on the back of the 545, this will need refitted as well, the 545 park brake assemble is not compatible with an MT643. there are no electronics required.. the speedometer, reverse lights, neutral safety are all the same from 545 to 643.





the other range of transmissions are electronic. your engine is mechanical however with the right equipment an electronic transmission can be installed anbd you will gain one or 2 overdrive gears along with lockup (significant upgrade).. this upgrade comes with a pretty high price tag and patience required to dial in the transmission..


allison 1000 / 2000 transmissions offer 5 or 6 speeds (2005 and earlier are 5 speed, 2006 and up are 6 speed).. and can be had with SAE3 bell housings.. they are such that they will bolt right up in place of the AT545.. no modifications to the bell housing area or transmission mounts.. if you have hydraulic brakes wit ha drum on the back of the trans then some modifications are needed for the parking brake.



the 1000 / 2000 are electronic and will require a wiring harness, a TCM (transmission computer).. and for your mechanical engine will require a throttle box.. the throttle box (TPS) has a cable which actuates electronics and tells the transmission how hard you are hitting the go-pedal.. typically it mounts in place of the mecahncial modulator that your AT545 uses...



there are companies (CAC(Custom automatic COnversion), and Defero are examples) that you can buy a whole package with a reman allison 1000 6 speed, computer, TPMS, and harness).. this is a $$$$ route to go..


you could also source a used transmission and then go to a 3rd party that does wiring / computers only (jason at transmissiontuner dot com) to source the electronics.. which saves some money..



Ive done an AT545 to MT643 swap on an IH DTA360
Ive done an AT545 to Allison 1000 swap on an IH T-444E
Ive never done anything with the 8.2

 

[cadillackid]

if ypou simply want to replace the broken AT545, LKQ in marshfield missouri still had some remanufactureed units with no core for $550 last time I chacked.. they were made for IH so will have a maximum RPM for shift at about 2600 RPM.. im not sure what the engine redline is for your 8.2, if its close one of those may be a possibility and is of course a pretty easy fix to get you back travelling again.. install it and put a big cooler on it and it will get you travelling again for a good while until you plan out your full powertrain swap

 

[Ghrasshopper]

Cadillackid thanks so much for all the information. This is way more than I had hoped to get and it gets me a new line on an eventual powertrain swap. I ended up just getting a remanufactured AT545 and having a shop swap it because it was the fastest easiest way and I needed to get my bus moved and get to work for the summer. If I had some more time to figure it out I would have tried to put a different transmission in but the parts store I ordered it from wasn’t very helpful when it came to modifications.

 

[CHEESE_WAGON]

If I had some more time to figure it out I would have tried to put a different transmission in but the parts store I ordered it from wasn’t very helpful when it came to modifications.

And they won't be, because most parts counter monkeys only understand what the computer tells them is there, I can't think about anything beyond that.

 

[cadillackid]

when a shop is doing it you have to find a custom shop.. cheese wagon is right , the regular parts counter guys often dont know themselves and so all they have is their screens to go on.


sometimes you get lucky and someone at an auto store has done what you are trying to do and will be ablw to help.. but honestly customizing school busses isnt something very many do.. ive been met with all kinds of reactions when it comes to ordering parts for ny red bus which is a custom swap-in and arguably a much more intricate computer integration than even the factory does.. as a result it means I have to keep note of which parts fit what so I can order them again.. ie that my neutral safety switch is from a 2001 GMC sierra with a diesel and auto.. that my allison TCM is from a 2008 GMC 5500 with a duramaxx, all of my belts on my DEV bus are non-fasctory sizes length due to the custom dual A/C.. so I keep a list of which belt goes where and the Gates model numbers of said belts.. so when i need new ones they are easy to find..

 

[CHEESE_WAGON]

Hence, why I say it's better to wait until you have a complete donor for a full powertrain or body swap. That way you know everything came from one VIN, year, make and model.

 

[johnbloem1974]

When I swapped my 545 to MT643, I lucked out with the guy at the International Dealership in Phoenix (we had broken down in Quartzsite). He was super helpful and if he didn't know the answer, he called his "Allison Guy" to find out. Between him and everyone on Skoolie , made a real shitty situation bearable!

John

 

[cadillackid]

Hence, why I say it's better to wait until you have a complete donor for a full powertrain or body swap. That way you know everything came from one VIN, year, make and model.

That’s all well and good if what you are building was ever built. In my cases it wasn’t.. or is so rare ( find me a dt 360 with dual AC and air brakes). That you either have to go with a lesser build than what you want or you have to build it yourself and take notes..

A 444e never was built with a 6 speed allison 1000/2000 factory. 5 speed yes, 6 speed no.

6 speed md3060 yes but very rare , I either had to pay top dollar for an amtran RE bus with a 3060 and 444e that I would then essentially ruin or have to make crappy driveable by doing a 545 swap to it.. or simply go buy new teams parts for a custom 1000 swap to my bus that yes is custom but money and time spent on my build with brand new parts versus having to build 2 busses to recoup costs and still have used parts...

Choice was clear do a custom build, take notes, and have exactly what I wanted.

This is quite common in the hot rodding world in which I’ve spent quite a bit of time before busses..