Allison Trannies!!! Help

Discussion in 'Trucks and Trailers' started by landscapingpoolguy, Dec 29, 2004.

  1. landscapingpoolguy

    landscapingpoolguy LawnSite Senior Member
    Messages: 822

    OK guys I need some advice,

    First off I have a 96 Int 4700 with the 7.3 dt444e engine and an Allison At 542 tranny. This tranny is bad. I inherited an Allison at 545 from a buddy, this tranny came from a Gas engine truck. Now after repeated conversations with different tranny guys they all tell me that no my bigger and better at 545 tranny wont work with my diesel 4700 because the shift points are different. Now when I go on they list the full specs for both trannies.

    Now both tannies are almost identical that I can see except for the option of the tourque converters, and the input speed ranges, my question is doesnt the tourque converter translate the input speed ranges? in other words, if I use the converter for a desiel setup for the at 545 shouldnt it all work just fine? the only other difference i can see is there are external cooler lines on the at 545 while the 542 has an oil sump pump system.

    Well if there is anyone that can add to this, or help me out please, I would appreciate the help, this is a costly part to replace, and I dont want to do something unless I have all the facts about these two transmissions and there compatability, especially since I have them both in my possesion already.


  2. lawnboy30

    lawnboy30 LawnSite Member
    Messages: 92


    Glad to hear your coming back. I guess you got good news on your back problems? Anyway, if ever you need help you can pm me.
  3. kc2006

    kc2006 LawnSite Silver Member
    Messages: 2,443

    If the shift points are the only difference couldnt you just have a custom chip made for the truck so it will A: shift different or B: reprogram it to be ok with the new shift patern? Just a thought. I don't see why the shift points would matter.
  4. Albemarle Lawn

    Albemarle Lawn LawnSite Bronze Member
    Messages: 1,544

    Generally a gasser is going to have higher shift points.

    You may be able to use it and just "wind out" your diesel, or as the RPM's get too high let off the gas real quick to inspire a shift, then throw more coal on her after it hit the gear you want.
  5. landscapingpoolguy

    landscapingpoolguy LawnSite Senior Member
    Messages: 822

    the Rpm's of the shift points for the gas tranny are in the 4- 5000 range, my 4700 runs at 3000 rpms at 70mph. I dunno I found a used at545 trans out of a deisel bus from the same 7.3 engine that I think im gonna pick up. only thing is the miles are abit high but its a heavyier duty trans all togetehr. unfortunaly my trans is a 542 which has a max gvw and hual rate of 21,000. I cant tell you how many times I go over that rating. The at 545 goes up to 33,000 gvw, so its a considerable upgrade.

  6. landscapingpoolguy

    landscapingpoolguy LawnSite Senior Member
    Messages: 822

    Ha I like that, " Throw more coal on her".

    UNISCAPER LawnSite Bronze Member
    Messages: 1,426

    The 545 is way beyond chip technology. It uses vaccum and not electronics to shift, making it more reliable. The shift points are critical because they are set off the optimum HP and torque necessary to accelerate the truck without lugging and bending push rods in the motor. Lug a diesel too much and they will stop and start backwards belching exhaust from the air cleaner and using the tail pipe as an intake.

    I just called my friends at the tranny shop we use because this thread peaked my curiousities.

    They said: "The AT545 can be completely rebuilt and changed to use on either gas or diesel. You can replace a valve body for around $500.00, or, completely redo that unit for $2,500.00 to $3,000.00. It is very easy to see those trannies to go well past 150,000 miles with out ever having been serviced."

    I hope this helps.....
  8. hosejockey2002

    hosejockey2002 LawnSite Bronze Member
    Messages: 1,195

    You must be thinking of the old 2 stroke Detroit Diesels. A four stroke engine can't run backwards. You could make a Detroit run backwards if you killed it starting out, but that wouldn't happen with an automatic.

    UNISCAPER LawnSite Bronze Member
    Messages: 1,426

    Hose Jockey:

    I have had a Mack, a Cummins, a Perkins and a Detroit all run backwards when they were lugged to much. In this age when they have yuppified technology and electronics, I'm betting they have sensors that won't wllow that, but two stroke of four stroke does not make a bit of difference in making them run backwards.
  10. hosejockey2002

    hosejockey2002 LawnSite Bronze Member
    Messages: 1,195

    Guess ya learn something new every day. In my years of driving all of the above (except Perkins) Detroits are the only ones I've seen run backwards.

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