Allison transmisson slamming in to gear at times

[D/A]

When I tow my 32'5th wheel at times after stopping I start to go and it reaches the rpm to shift it does but just slams into gear I am afaid its going to break something. It never does this solo and only sometimes when towing. I am not aware this is going to happen so I can let off of it. It scares the heck out of me that its going to break and leave me stranded. I had tranmissons in the past shift hard with shift kits etc. This transmisson is stock and slams so hard it shakes the truck. Any ideas what might be wrong would really help. Thanks PS>02 Duramax

[Buck]

My '01 had a bad 3rd gear slam when towing, it would launch a cup of coffee out of the cup holder and onto the floor :eek:

My '05 LLY has started to do that this past weekend towing but not near as harsh as the '01. Didn't matter if it was in tow/haul or not.

Past conversions have lead this to be "normal" as stock trucks owners have reported the same problem.

[D/A]

What I see is this it mosly does it on 1-2 shift and only at times, the problem is you never now when. It really seems like its going to break either the transmisson or rear end or both this sure isnt good. I dont know why it just does it sometimes not all the time. I have always had the normal things like you feel like your getting rearended when sitting at a stop sign etc.

[jcummins]

The last 100 miles of a 1600 mile trip, towing fifth wheel, my transmission did this. A month later I did a short haul, and it did it consistently again. Never happened if I wasn

[Grayfox]

There is a tsb. for this problem... it's a reflash for the tranny. Do a search on this site and you'll find plenty of info. on the reflash

[D/A]

Thanks for all your help. I will call the dealer about the reflash. Can you tell me what a SC III is. Thanks again

[jbplock]

Originally posted by D/A:
Can you tell me what a SC III is. http://www.suncoastconverters.com/

[Jim Brzozowski]

Ya know, if you could get your transmission to slam into every gear every time and not slip, there would be a bunch of people standing in line to buy it. High horsepower and slipping are the real destroyer of transmissions. I have a brother in law that hoped up his tranny in his truck because he tows heavy trailers during the farm harvest season. It chirps the tires everytime it shifts, he now has over 230,000 miles like that and the trans has never failed. However he has had to replace the rear gears twice now. No its not an allison, its an old turbo 400. Until someone figures out how to trick the computer and make the clutches do what you want and make it selectible, someone will always complain. Personally I when running empty and easily accelerating prefer not to even feel the shift. When racing you want it to lock up almost instantaneously so you don't loose time. It all depends on what you want. In stock trim you should not have any slam shifts anytime. Trying to duplicate the problem with the dealer riding along is another thing. Its like the truck knows not to mess up when someone else is watching, right?