Put a new diff in (went from 3:43 to 3:72) when truck changes to 2nd transmission slips (no noises) if I put in manual Reverse and 1st fine, even holding brake and giving gas no slips. I tried starting in 2nd and 3rd high rpm no power. When use OBD2 reader shows gear ratio 8 which is shows like an error limits are 1-5 according to reader.

I have dropp8the transmission pan no metal shavings or burnt smell.

Thinking of replacing the TCM, I've pulled it out and ohmed the solenoids (all seem good).

I have access to an autel maxisys odb2 reader that lets you turn the switch solenoids off and on. When I do this I don't hear any noise, I tired this on a 99 and a 2014 and I can here them click on and off.

This is driving me crazy! Any help would be greatly appreciated!

 

changing the gear ratio requires reprogramming the PCM/TCM and EBCM, or it won't shift or brake correctly, and possibly damage the transmission.

 

We just bought a Diablo tuner because someone else told me it needed to have the gear ratio changed. Can you tell me if you think this will program it
https://www.summitracing.com/parts/dbl-9245

 

no idea. ask their tech support.