I'm having some serious problems with my transmission! Since January I've had it rebuilt new TC, new solenoids, new valve body with wiring harness, new neutral safety switch, new ignition switch, new PCM... I've replaced the solenoids 2 times! My problem is that it keeps going to limp mode reverse, 2nd and 3rd only... One day it does perfect the the next day it won't... This is my means of transportation and I drive 100 miles a day for work... Any information would be greatly appreciated... Thanks in advance...

 

From the 4L60E Common Problems thread:
Since you have replaced the solenoids and the wiring harness, I would suspect either damage to the main wiring harness from the trans to the PCM. You may want to start by running a new wire for the shift solenoid A control from the transmission connector to the PCM to see if that works.

The wiring diagrams should be somewhere on the forum. If not, let me know and I'll try to get it uploaded in this thread.

*EDIT* - Check out the thread below for the wiring diagram. You are looking for the light green wire in cavity A on the transmission connector that runs up to Connector 2 pin 6 at the PCM.

P0753 - Shift Solenoid A Electrical

 

Since my last post I have checked all wiring to and from the trans and it is all in good working order... I ran a wire like in the diagram and it is still doing the same thing... Sometimes the trans works perfectly and some times it goes back to limp mode... No 1st or 4th and I have to manually shift from 2nd to 3rd and manually downshift... I have power to all wires and everything is new in and around the trans... Anymore ideas would be greatly appreciated...