Allison Transmissions Help!!!!

Discussion in 'Mechanic and Repair' started by landscapingpoolguy, Dec 29, 2004.

  1. landscapingpoolguy

    landscapingpoolguy LawnSite Senior Member
    Posts: 819

    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 IndustrialAutomatic.com they list the full specs for both trannies.
    http://www.industrialautomatic.com/html/at5451.htm
    http://www.industrialautomatic.com/html/at542.htm

    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.

    Thanks,

    Chuck
     
  2. UNISCAPER

    UNISCAPER LawnSite Bronze Member
    Posts: 1,426

    The torque convertor simply applies a lock up similar to letting the clutch out on a stick shift tranny. The torque convertor will engage at the same RPM weather you run a gas or diesel engine. If one was higher than the next, you would have the effect of dumping the clutch when it locked up.

    The shift points are when the tranny senses engine torque is optimum to transition to another gear.

    With your DT444 cubic inch engine, shift torque is going to be sitting right around 1500 RPM give or take, on a vaccum shift tranny. With a gasser, torque is optimum around 20,2200 RPM.
    There has to be a way to change the shift points inside the tranny, usually through a valve body and/or set of vaccum switches.

    So, can you find a tranny shop willing to make some valve body mods in your tranny? If you have problems call the good folks at Oceanside transmission (760) 722-7176 and explain your problem. They can handle anything you throw at them.
     
  3. landscapingpoolguy

    landscapingpoolguy LawnSite Senior Member
    Posts: 819

    Thanks im keeping my options open, the truck is 10 years old and I really cant justify dropping 4 grand for a trans into it. Besides I need a few new toys this spring.

    Chuck
     

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