Allison Tranny slamming downshift

[socaltoolguy]

I posted this question once before and got an answer from John Kennedy but now I can't find the post. After pulling my fifth wheel and coming down to a stop I go to take off again and the trans hasn't shifted back into first. All of a sudden it bangs into first. It feels like getting hit from behind. It has only happened twice but both times I was pulling a trailer and taking off from a dead stop. I wasn't coasting but had come to a dead stop to wait for traffic to clear. Has anybody else had this happen?

[DmaxMaverick]

This is an old issue, corrected or identified long ago.

If you haven't had the most current PCM/TCM updates, do so. It may take care of the issue altogether, along with some others you may not be aware of. Of course, since you are out of warranty, you'll have to pay the dealer to do the update. Should be less than an hour's labor for a competent tech.

If above doesn't apply....
Are you a "two foot driver"? When you come to a braking stop, with any go pedal input, the tranny may not downshift. This may attribute to an ocasional failure to downshift to 1st. With some TCM programming, the TCM needs to see zero go pedal input, brake input, and zero forward speed (or any combination) to shift into 1st. Some of the programming updates made the TCM a little less critical.

Try that out, and come back with your results.

[socaltoolguy]

Thanks a bunch for the reply. No I do not drive with two feet. I can't stand to see anybody do that. My wife used to but I razzed her enough that she quit. I am about due to take my truck in for service so will get the latest updates. The last time I asked about updates they kind of side-stepped the issue. I am going to go to a different shop this time. Thanks again. Ray.