If this has been explained, pardon me. Direct me to the thread and i will read gladly.
I installed a 1993 4l80e behind my 6.0 using an 2001 pcm. I have a PSI harness built for the 4l80e. The transmission will not shift. Not sure if it is taking off in 1st or 2nd but it is not shifting. I know that pre 1996 4l60e transmissions are not compatible with ls pcm's. Is this what i am dealing with?

 

I doubt it. The only electrical difference is the original force motor that came in the '93.
Very, very common on swaps is no 12 volts, ground problems, and pcm signal problems.
Starting off in 2nd or stuck in second is limp mode, it happens when the transmission has no electrical.

And you're not the first one with a high dollar, premade, plug and play harness that didn't play.

 

Thanks for the information!

 

Speedo works, just no shifting.

 

I need a little more help guys. Pink wire in the round plug is getting 12 volts. Also, had the tuner look at the tune, the proper "segment" or tune is in the computer for the 4L80e. So now, what is my next step. I was told that my tranny is pre PWM and I needede to purchase some harness to go in it to make it wirk. Help Please!!

 

What happened in 93 was GM changed the case plug and inside ( the trans) wiring. Most likely
you have the new plug, don't think you could plug into it if the old case plug. To be sure, look at the
plug in the case, should have 4 contacts top row, 1 on the sec row, and 6 on the bottom. The contact
on the 2nd row should have the +12. On the bottom row, counting from the left, contacts 3, 4, 5 have
voltage, they go to the pressure switch. Your shifter moves the man. valve, which (when engine is
running) directs fluid to the pressure switch, depending which gear you selected, puts a ground out to shunt
the voltage, and tells the ECU what gear you commanded. If the ECU cant determine what gear
is wanted, it will go limp mode, 2nd and rev. 1994 they changed the force motor, and the spacer plate
got some diff holes, and the force motor also got a diff HZ #. How that affects things I don't know,
or if you need or have the new motor. The newer FM may be black.

 

I seriously doubt PSI would build a harness for the old style connector. The old style has a screw in the middle. Is this what you have or do you have the new type?

Where did the transmission come from? Did you ever drive it before this swap?

 

No I do not have the old style plug, it does not have a screw n the middle. My trans mission does have the new style plug. The transmission was a new rebuild prior to me putting it in my vehicle.

 

do this. It will tell you if the problem is the harness/PCM or the transmission.