07 Pontiac g5 - bad shifter cable for auto trans?

Maintenance/Repairs
1

Hello everyone, I got a feeling that my shifter cable is on it’s way out but I want second opinions before I take my car to have the transmission rebuilt.

So the main issue with my g5 is that sometimes the car will drive forward/reverse and at random, you’ll hear very loud and fast clank/clunking noises which the car would slow to a stop; the RPM needle still moves at a steady and normal pace when driving/reversing. The problem doesn’t happen in Neutral unless you change from drive/reverse. I went to check out to make sure it wasn’t something with the CV joint I replaced and also noticed that when I had the car in Park it moved backwards a way on a flat surface.
The check engine light also does not appear.

Any thoughts on what the problem could be?

2

If you have the facilities to do it, you could carefully watch the linkages from the shifter to where it meets up with the transmission as a helper shifts the lever. You might be able spot a clue, like a bushing that is loose, a bracket that has come unhinged, etc. But that’s about the best you can do as a diy’er. This is probably going to require a shop inspection to determine what the actual cause is. Suggest to not simply presume this will require trans rebuild. Wait to see what the expert shop guy says. I think you’d do better by visiting a transmission specialist for this. Ask your normal shop staff who’s the best transmission shop in town.

You’ve checked the transmission fluid level, right?