My son has a 1994 Z28 350 with a 6-speed manual transmission. In the last month we replaced the tranny and engine mounts. When we got the car back from the dealer last week, there is now a great deal of vibration in the shifter and it intermittently moves up and down. Also intermittently, it will not shift into 3rd gear. All other gears seem to be working fine right now.

This only started happening when he got the car back from the dealer after the motor mounts were replaced last week. There is no grinding, but something is going on. The dealer said it must be something internal in the tranny and without digging into it, they don't know what it could be.

Thought I would post here to see if anyone else has encountered a similar problem and if so, what it was. If not, maybe someone has an idea of what the issue may be. I am not mechanical and I hate to throw more money at the dealer to figure it out. The guy he bought it from said it had a new tranny and clutch, but my son being a teenager didn't get any paperwork and I suspect that he was not telling the truth given other issues we have found.

Appreciate any help or direction anyone can provide. He continues to drive it for the moment, but I am not sure if he is doing more damage by doing so and if it is better to park it. Thank you.