Hey all, I recently swapped an LT1 out of a 95 Camaro z28 into my Chevy Silverado K1500 pickup. I had the 5.7 TBI before, so the swap was pretty straight forward. The only issue I am having now is with the transmission... I used the tranny from the Truck, which is a 4L60E, with the 4wd transfer Case. Bolted right up, used the trucks flex plate, starter, and torque converter. I had the Camaro PCM tuned to match the motor to my truck's drivetrain. Here is what's happening:

when you initially start the Truck and put it into drive, it starts in first gear, shifts into 2nd nicely, shifts into 3rd nicely, then stays in 3rd. Won't Down shift at wide open throttle, nor will it down shift at a stop. If I put it into 2nd manually, then back to drive, it will start in 2nd, then shift nicely to 3rd, and stay in 3rd. If I put it in Park, shut the truck off for 30sec, start it back up and put it in drive, it starts in first again and then does the same thing.

Initially, I thought it was limp mode.. But limp mode wouldn't start in first gear and do those two initial shifts... I tested each solenoid individually, and they all work. My vss is working, for I am getting a good reading on the speedo which is fed from the PCM. The TPS is working properly,with a nice linear increase of voltage from 1-5v. I have checked continuity on every wire from the tranny plug back to the pcm and they are all good. My pink voltage supply wire to the solenoids has power.

I am running out of things to test... Motor runs like a champ, and I just want to be able to use the New horsepower I've gained!! Haha anyone have any idea as to what this could be? Thank you

 

You didn't change the engine or the trans; however the tune was changed and I always suspect "the last thing changed". Plus you have very thoroughly checked the trans and thought of the likely things that could go wrong in the trans.
You are correct that it does not sound like limp mode.

The PCM has shift tables for Normal, Performance and Hot. I wonder if the trans temp sensor is readying way high and putting the PCM into Hot mode and your Hot shift tables are screwed up.
Do you have a scanner to read the trans temperature and scan for any codes?
Can you upload the tune?

 

I will contact my tuning guy and ask if.he can send me the tune. In the meantime, no I don't have a tech 1, nor do I have access to one unless I go to the dealer. The scanner I have is obd 2 and being a 95, the obd2 scanner doesn't plug in. I can run to shmucks (oreilly's) and hook up their scanner,but will that be able to tell me the information I'm looking for? Thank you for the quick reply by the way.

As I said, I used the transmission that was originally in the Truck, and it worked perfectly before the swap. Now in no way am I saying there couldn't have been a freak coincidence that the something failed in the tranny right when I did the swap, I am just pointing out that I know that the tranny worked well right before the swap.