Tranny slipping!!

[Barc]

Has anyone had any experience with their Allison slipping?? It seems to be most frequent after coming to a stop at a light or stop sign - when you take your foot off the brake to accelerate it hesitates just for a second and then kinda bangs into gear. It will also shudder when taking off from a stop - I have a couple of friends who have changed out their tranny's and I hope I am not the next one!! I checked the fluid and it is right to the top of the "hot" full line - NOT overfull - just exactly where it should be - tranny was completely serviced about 10,000 km ago - truck has abour 107,000 km (67,000 miles) Any ideas??? Thanks

[DmaxMaverick]

If you haven't had the PCM/TCM updated, you need to. There is a known issue involving the 2-1 shift that the software addresses.

The "slip" you are feeling is the tranny's failure to downshift to first during a stop. When you take off, the computer realizes it is in second, then downshifts, causing the "bang".

This will happen much more often if you are a two-footed driver (right on the go pedal, left on the brake. The PCM needs to "see" a brake input and zero throttle input to shift into first. Even if you've had the updates, it will happen when you drive this way.

Cheers.

[mark45678]

I think Dmaxmav has hit the nail on the head! if the tcm see any input from the tps it will not down **** correctly! try comming to a stop with your foot just barely on the go peddle and let off the brake I bet you get the same feeling ...Bang it down shifts from 2nd to first under load and takes off ! :( just a small price to pay for growing pains....

[Rebel_Horseman]

Does anyone know if there is a TSB for this issue? My truck is having the exact same phenomenon going on and I was getting worried about it myself. It does it to me more regularly when it's cold and I'm in traffic. My truck is going to the dealer tomorrow to get a new slip yoke, u-joints, and speaker installed and I'll get them to update the TCM if I can tell them what needs to be done.

Reb [><]

[ram/tx]

Rebel---do a search on trans downshift, or something like that an you will find all kinds of reading an part numbers to take to the dealer. I think they have to reprogram the TCM and PCM to fix the problem, I had mine done and it made a big difference in the truck. You can also go the the GM site and punch in you VIN# and it will tell you what updates you need. But try the search. Lots and lots of information on this subject.

[Rebel_Horseman]

Here's an update for ya'll. I called the dealer a few minutes ago and they told me that the tech screwed up the slip yoke that was on my truck when he was trying to take it out, then when he tried to put the new one in he realised that it was not made for the Allison! :mad: Now I have to be without my truck tonight. He's calling the insurance peop[le that handle the aftermarket warranty work to see if they will cover a rental. if they don't I'm going to make the dealer foot the bill.

Reb [><]