Trans bump when stopping & taking off


New Member
Allison MAN I have a 2001 2500HD with the duramax and allison. When comming to a stop the trans has a harsh bump just before it stops fully. When starting to move without using the accelator it seems like it is in 2nd gear,when slightly pushing the acclerator another bump occurs and it seems (almost sure)that it is downshifting. From that point on it is normal untill comming to a stop again.I am a retired mech and dealt with throttle position sensors on sedans which acted somewhat the same. Any shift point adjustments? Supposedly the computer was updated long ago and taken to several dealers under warranty but no one had an answer. Thanks in advance for any direction. Also rear end & trans have been serviced
Trans bump when stopping & taking off

Allison man is no longer answering his treads(retired), but there are a few others that have been giving great advice. I myself have an 02 2500HD same setup and had that problem last april. The dealer found a recall on the output yoke from trans to driveshaft.Seems some were machined to close to tolerance and a different material and they create a binding effect when stopping/starting,mine only did this when taking off from a stop, though.If you read back in allisonmans treads he list his EMAIL and you can email him. I have emailed him quite alot with another problem, It might take a few days for him to reply but he always has. Hope some of this helps LEE