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Allison Question

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Hey folks -


Hopefully I can describe this correctly: I have a set of speed bumps installed on my road here at home. I usually let the truck idle over them and then gently get back on the accelerator when I'm past them. I've noticed a few times that when I get back on the accelerator, the torque convertor doesn't lock, the engine spins up to 2500RPMs or so, and the truck doesn't accelerate.


It's sudden, and all I have to do is breathe off the accelerator for it to get moving again. I'm not sure if the engine will keep spinning up because I always flinch off the accelerator. I haven't been able to pinpoint the exact conditions for it, but it seems to be a slow idle/coast transitioning to (an attempt to) accelerating. I also can't reproduce it at will, so I haven't brought it in to the dealer yet.


Has anyone experienced anything like this? Is there something in the Allison's programming that'd cause it to react like this? Should I be worried?


Specifics: 2005 Sierra 2500HD, Duramax, Allison. Just over 1000 miles (brand new.)





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It sounds to me like your rolling at just the right speed that your a little fast for 1st gear, but a little slow for 2nd. Your engine will rev up (usually not to 2500rpm though) in 1st gear only to quickly then decide your moving fast enough for 2nd gear and shift. Usually when mine does that, you get a pretty good jolt when it finally revs fast enough to catch 1st gear.


Your conditions may be different, but its normal for the any of the trucks with the allison to have a little jolt when you get back into the gas too fast at about 10 or so mph.

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