Transmission shifted to reverse while traveling highway speed

[junkyardjack]

First post here, hopefully this is where it goes. Mother-in-law was driving my 99 k2500 suburban into town. She started to slow down to turn and instead of hitting the turn signal shifted the transmission into reverse or park. Left a patch of rubber on the passenger side of the highway. Didn't sound like there was grinding or whirring sound, just tires squealing. Makes me think she put it in reverse. Took it for a test drive when I got home from work. No crazy noises in any gear or direction. There is a driveline clunk when shifting between park reverse and drive. Not sure if this was here before. There is likely about 30° of rotation in the drive shaft between reverse and park with the brake Applied. 4L80E transmission, uncertain rear end, fancy push button transfer case with four-wheel auto. Anyways where do I start looking for damage? 133,000km/ 82600 mi. 7.4l / 454

 

[GoToGuy]

U joints, ring and pinion clearances play, drop pan new filter, look for impending damage debris in pan. Change inspect fluid in transfer case.
Driver awareness retraining class.
That's what I would start with.

 

[Schurkey]

"I" would start with driving the vehicle for a week and see how it works. Verifying that the fluid isn't burnt might be nice.


Forty years ago, a guy I knew dropped his TH400 in reverse at highway speed--the car was a '67 Cutlass Supreme with poor brakes. He panicked, threw it in reverse to avoid hitting something--another car, a deer, a tree. Trans took the abuse and gave no problems afterward.

I'm NOT saying this is recommended...

 

[Erik the Awful]

Inspect the u-joints, driveshaft straightness, and carrier bearing. If that's all okay, drive it for a week or so.

 

[Caman96]

I’ve mentioned this before, and yeah we were young and stupid, but a running drivable car could be had in the 70’s for $50.00, but I’ve been in cars and personally floored it(need high rpm’s) and dropped into reverse doing what we called RD’s . I can’t say I remember it damaging the transmission and doing it multiple times. Of course nothing in our lives was long term then, so hard to say what effects it had…long term.