Got back from Home Depot last night with a trailer load. Went to back the trailer up my driveway and the Allison would kick out of reverse after about 4 seconds and 'Range Shift Inhibit' would show up on the DIC. :( Had to drop the trailer in the street and move it around with the little pickup.
Let the truck sit for about an hour, started it up and put it in reverse. After about 3-4 seconds it would drop out of gear and the RSI message would be on the DIC. I could shift to netural or park and back to reverse, it would go into reverse for about 3-4 seconds and pop out again. It would do it every time I tried. It would move the truck backwards, but only for about 3 seconds each time.
This morning on the way to the dealer, it would shift real hard at around 3k+ on the tach.
After reading on here I was thinking NSBU switch, but the dealer called after looking at it and wanted permission to drop the trans. There goes all my TranSynd Censored

Anyone care to take a guess what broke?

Thanks

DalDMax

I would tell them NO and try a NSBU first.

Well they said that the NSBU was ok.
They tore into it and are saying that the C3 Clutch Pistion is leaking and causing the other clutches to slip or not engage.

Is this a common issue with the Allison or just my normal bad luck ??

Anything I need to be concerned about after they get this taken care of ?

Thanks!

DalDMax

I bet you will see a new NSBU switch on your Alli when you get it back. Hmmmm.

we had one do the same thing here at work. but it only had around 8k miles on it. it had a large piece of the piston seal missing!

I am going through the same thing right now, 80k miles. When cold it will go limp and have to be shut off. Last week it got cold here after it sat all night I started it and it went from high idle back to low, so it ran for 10 min. Then when backed up and tried to go forward it finally threw the cel, so i drove it to the dealer at 25 mph and never shut it off. They said they can not duplicate the problemand the codes(which I didn't get from them) don't tell them whats exactly wrong.. The NSBU was swapped out by the same dealer a month ago. This sucks cuz it's getting expensive. I really think that most dealerships suck! By the way both filters were done this summer and new fluid put in. When my buddy and I dropped the pan he was impressed as to how clean it was. I am frusterated, I take good care of my truck and now I am lost!! I am about ready to trade it in and let some poor wholesaler get it.

Do you guys think it could be that clutch piston? And for you alli gods how much does something like that cost, I am guessing alot if the trans has to be torn into....

Well got the truck back from the dealer a couple of days ago, just haven't had a chance to post.
The invoice shows:
Clutch Assy, 3 5 and Reverse R&R or Replace
Filter
Filter ASM
Dex 3
Gasket Kit
Piston - part # 29541530

Doesn't look like they replaced the NSBU

Truck seems to be running as good as ever!

Thanks

DalDMax

I would have told them to refill with TranSynd if that's what you had in it when you took it in. :)