Allison 5sp: Transmission help!!

[nshadday]

Hello Everyone, I have a 2001 GMC 2500HD Duramax LB7. I have an issue I would love some guidance on. When using my EDGE CTS Tuner in TOW mode. The transmission will pop out of 5th gear and the engine will redline for a second or two. Then it will lock into 4th gear and will not return to 5th gear unless I pull over and clear the codes. This happens when I'm pulling my 9klb toy hauler up a steep hill. Addtionally, If i place the tuner in "performance" mode it will do the exact same thing if I'm already at highway speed and i attempt to accelerate quickly. I have reflashed the programmer and even downloaded the lastest updates. This has been going on now for about 6months.

 

[coker6303]

post up the codes

 

[nshadday]

p0700

 

[Mike L.]

Code # ?

 

[coker6303]

P0700 is just saying there is a problem. Should have been other codes in the TCM associated with the issue?

 

[Chevy1925]

im hearing "limp city". if thats the case, you dropping to 3rd gear, not 4th and bascially your trans is dieing fast

 

[nshadday]

TO be honest I dont remember seeing any other codes. I'm currrently deployed overseas so i can't look into it further right now. With the information I've provided. Are there any ideas? I have a mechanical buddy who mentioned the possibility that the tuner creates to much power for the transmisison which causes the transmission to go into a "safe" mode? I'm not sure if that is even possible. Just looking for help

 

[nshadday]

I can see which gear is selected on my tuner. The truck is in 4th gear and the torque converter is locked

 

[04D_MAX]

sounds like its slipping

 

[nshadday]

So what is the cost to have a transmission repaired??? Any suggestions on a good place in Washington State??

 

[Chevy1925]

without actual TCM codes, all we are doing is guessing. get us those and then it can be determind what needs to be done

 

[mike diesel]

Its obvious the trans is going into limp mode from too much power...

I highly doubt there is anything wrong with the trans other than it can't handle the power that high.

I would bet the code is for 5th gear incorrect ratio.