I have a 2007 Tahoe. Automatic Transmission. On the way home I heard this "thunk" from the engine compartment and then the engine reved up. Car would not move. I slowed down, it clunked again, and then starting going. Turned up the street to my house, and the car wouldn't move. I tried moving it to Park and Drive and would not move. When I moved it to 2nd or 1st gear, it would move.

So Reverse Works,
First Gear Works
Second Gear Works
No Movement when in Third
No Movement when in Drive.

I checked Transmission Fluid Level and it is fine. Looks clean and not burnt. No Status/Warning Lights.

Definitely hear the transmission engaging when moving selector to 2nd or 1st, but not Drive or 3rd.

Any thoughts on what might be its issue?

 

I'm going to call a broken forward sprag. Once it breaks, you lose 3rd and 4th. 1st, 2nd and Reverse still work. It's an inexpensive part but you have to remove and disassemble the entire transmission. I did the work myself. Still spend $600. I had 202K miles on it so I figured I would refresh some internal parts. Everything was within spec but I replaced the clutch material and steels as well as all bushings and a few other parts. Basically, It's a hybrid between a 4L60e and a 4L65e. Has 329K miles on it now.

Check this site for more info:
https://twincharlotte.com/30-common-...-charlotte-nc/