Allison 5-speed Automatic

[ardmore]

I am having intermittent problems with the up-shift from first to second in my Allison 5-speed automatic in my 2002 Duramax. It is a very violet shift, about like revving up the engine and poping the clutch on a straight shift, feels like the transmission/rear end are going to fall out. Does this about once every 15 shifts or so, only when I am in the Tow/Haul Mode and pulling my 5th wheel. Been unable to duplicate the violent up-shift when I take it to the dealer and dealer will not change out the Transmission Control Module (TCM) or any other transmission elecronics to try and isolate the problem because GM engineers will not okay the parts swap in order that the dealer can be paid under the warranty. Anyone else had/having this problem?

[Turbo Al]

Ardmor: Hi and welcome to the forum. If you run a search over on the 2001HD/3500 Trucks & Drivetrain forum you will find a couple of fixes for this glitch.
1. Shift the trans down manually - one gear at a time, a few times (to dead stop).
2. From approx 50 mph put the shift lever in "1" and let it come to a complete stop -- and it will do so ratter quickly so pick a quite piece of road, do this a few times.
Most of all use only one foot for brake then gas pedal & come to a complete stop.
This truck has a slow learning curve and the above just speeds it up.
I have done both with no ill effects to trans, but I prefer the shifting manually one gear at a time over the 50 mph dump.
Turbo Al