PDA

View Full Version : Wierd Allison behaviour



Wont Goof Again
03-13-2004, 04:38
I currently own a 2002 Silverado 4x4 D/A CC LB. Normally the Allison will not lock the TC until around 50 MPH either in 4th or 5th (unless tow/haul is enabled of course).

Occasionally (this has happened about 5 or 6 times over the past year), the Allison will lock the TC below the 50 MPH mark - usually around 40 MPH. I know it is the TC locking because the RPMs drop to around 1200 and I'm already in 5th, so it's not shifting again. Pressing on the accelerator does absolutely nothing to the RPMs. When I release the accelerator, RPMs remain the same for about 1 - 2 seconds; then it's like the Allison has figured out that the TC shouldn't be locked, it unlocks the TC, and RPMs drop.

I can't predict when it will happen or reproduce it. Most of the time, it has happened when I have been accelerating moderately from a stop and am in the process of easing off the accelerator in order to maintain my current speed. Other than this, the truck works great!!!

More Power
03-17-2004, 08:44
Check to see if any TCM updates are available for your VIN, and you might consider servicing the trans. Are any DTC codes being set?

MP