[2000CAYukon]

No 3rd can be:

- 3/4 Clutch pack is toast
- 2-4 Band is not being released (Servo)
- 3-4 shift solenoid, 3-4 shift valve

and other reasons. The fact that the fluid is foamy and overfilled is not good either.

Driving it while the tranny is slipping is not a good thing. It might be a good idea to have the pan pulled and inspected.

Good luck.

//2000CAYukon