Allison AT545 Reverse Problems

Discussion in 'Class A / Diesel Pushers' started by Flomuse, Sep 18, 2015.

  1. Flomuse

    Flomuse Junior Member

    I tow a 9,000lb Airstream trailer with a 1998 International "box" truck powered by the T444e Navistar engine. The transmission is an Allison AT545.

    Until now, my only complaint is that I should have bought a truck with more guts -- our 4700 was built for urban deliveries not over the road use.

    Recently, my transmission has become reluctant to engage reverse. Shortly after recognizing that problem, I noticed it was shuddering in reverse. The shudder is a low power thing and disappears when I apply more power.
    Other than that, the transmission seems well behaved in the forward gears.

    I was 3 service intervals overdue for fluid and filters when I took it in for a diagnosis. The tech found the fluid to be in "poor" condition and "swirly with metal and a lot of clutch material". But again, a fluid change was horribly overdue at this point, an accumulation of gunk was to be expected.

    A test drive showed the electronic modulator to be working properly.

    The pressure test saw:
    30 psi reverse signal
    30 psi main pressure in reverse
    150 main pressure in neutral and forward

    They concluded that I should spend $3,200 to have a Weller remanufaction unit installed.

    Money is scarce. I can manage the transmission problem for now, but I wish I could have gotten them to speculate on what's going on inside that tranmission. That sludge, for example, is the accumlation of perhaps 3 service intervals. Were they keeping that in mind when the pronounced my transmission effectively dead?

    A thorough flush might be expensive, but it might be a good investment if it produced an improvement or at least a little more information? Perhaps I can squeak a few more thousand miles out of it.

    I'd appreciate any knowledgeable opinions.

    Thanks in advance,
    Allison AT545 behind a T444e Navistar in an International 4700 pulling a 9,000lb trailer.
  2. dbarton291

    dbarton291 Senior Member

    You have a failed fourth clutch. That's why the reverse pressure is only 30 PSI. In neutral, first clutch is on. Select drive and you have forward and first clutches. 150 psi is normal. When you select reverse, first and fourth clutches are applied. Fourth has worn out and is leaking pressure. That's why the drop in pressure. The debris is most likely the failed fourth clutch material. You can get an Allison ReTran and get a factory remanufactured unit with an Allison warranty and not invest any more money than for the Weller unit.

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