Chevy Ali Trans Question

[CB1]

Two weeks ago I was pulling a 4000 pound trailer with my 2002 2500, duramax with 55,000 miles. when I pushed the tow/haul button the trans shifted very hard and the trans stuck in 4th gear and the service engine light went on. I pulled over and shut the engine truck started it back up and it was good as gold. I took it to the dealer and they told me the only thing they found wrong was a heater hose was loose. One of the codes I had read ealier said wrong shift (don't remember the exact number for the code). The dealer cleared the light and the truck ran fine. This past weekend I drove up with the trailer to a campground all fine. On the way back going up a hill, the truck shifted hard again the check engine light went on and the trans stuck again. I shut the motor off about 5 times and restarted and the truck finally when into gear before that the shift indicator light around the "D" would blink and the car would not move forward. I finally got the truck to move but it appeared it was starting off in 4th gear (NO Torque). Then the truck ran fine for over 100 miles. I went to drop the truck off at the dealer and I think the trans was slipping a little when I accelarated onto the freeway.. What do you guys think?
Online

[dieseldog]

Your trans went into limp mode. I would guess the code you read was PO735 Incorrect 5th gear ratio. It means that the trans was slipping in 5th gear. Do you have a programmer on the truck? Trans needs to be freshened up.

[CB1]

Yes, I have a hypertech programmer, I took it off before dropping it off to the dealer... So what do I do to clean it up.

[dieseldog]

You mean what does it take to get cleaned up and covered under warranty?
Its not GM/Allison's fault is it?
You turned up the power with a programmer and now the trans fails, I'd say its your baby now.
I think you should step up and put a triple disc convertor and shift kit in it, that way it can handle the power that you are throwing at it.
This is a good thread for all the guys that say hypertech's are trans safe.

[24sleekenforcer]

One comon problem on the allison trans is the range switch (park/netural switch). When it goes out the trans does not know what gear to select, was the code P0708 .

[sigepmock]

Yep sounds like you "limped" the trans. Once it happens once the damage is done and it wil happen again. See what the dealer says. I believe the clutchs have been damaged and the tranny will need to be rebuilt. If you want to keep running the programmer....better step up and have the trans built to handle the power. If you don't mind losing it and your conscience can handle it see what the dealer does to fix it. Chances are they will read the PCM and see that the files were recently modified and claim your warranty is void or you might get lucky and they may fix it for you for free. Either way I think you're gonna need some tranny work.
Chris

[Lightning]

On another note, you should be running the Transynd tranny fluid in there - much better then the stock stuff. Do some searching on thedieselplace.com There is more info in there then you need would imagine.

[CB1]

Just got back from the dealer they told me that the codes were erased when I disconnected the Hypertech system. They told me to drive it without hypertech and bring it back if nec..

[Daytona100]

Did you check the fluid? Pull the stick and see if it,s been overheated. Also smell it and see if it looks burnt. If not its probably just a solenoid or electrical.