Transmission Problems

[93mx6lsv6]

A buddy of mine has a 1995 C/K Pickup Extended Cab Z71 with automatic transmission. The transmission was rebuilt about 10,000 miles ago but he is having problems with it going into 3rd and 4th gear. It drives when you put it in 1 or 2, but when in drive it will not shift into 3rd or 4th. Reverse works fine and so does the 4wd. He was told something about some solenoid that is used for 1 and 2, then 3 and 4 and then reverse, and maybe that the solenoid has gone bad for the 3 and 4. Does anyone know anything about this or what else it could be? Thanks for any help in advance!!!

[2000CAYukon]

With the gear selector in Overdrive and the tranny in 2nd gear, 1-2 Shift Solenoid is Off, 2-3 Shift Solenoid in On, the 2-4 Band is applied, forward clutch is applied and the forward sprag clutch is holding.

To shift to 3rd, the 2-3 solenoid is turned off, the 2-4 band is released, and the 3-4 clutch is applied.

If the 2-3 solenoid or 2-3 shift valve is stuck, then it would not shift into 3rd. Of course, if the 2-4 band is still being applid (servo issue) or the 3-4 clutches are burned, it also will not shift into 3rd.

From 3rd to 4th, the 2-4 band is applied, the forward sprag clutch is released and the 3-4 clutch should still be held.

Is the check engine light on? A bad solenoid or shift valve should set the light. Not sure if bad 3-4 clutches will set the light.

//2000CAYukon