1991 GT transmission trouble

So happy to have found this forum.
I blew my manual transmission last week and my mechanic found me a used one and installed it. Since then I am having two recurring problems. About half the time I engage first gear, I get either a clunk or a thunk. The thunk is not as loud as the clunk. A few times I have attempted to shift from 5th down to fourth or neutral and it seemed to catch on something, and I had to fight with it. My mechanic fiddled with it for an hour yesterday but both symptoms are still present.
He now intends to drain something called a master cylinder. I don't have a good feeling about this transmission and would appreciate any input.


Thanks, Many Crows

I guess he thinks the clutch isn't engaging, and plans to do a pressure check on the Master Cylinder, (The big round thing going into the dash and has a resovuir on it for the brakes) Probably the wrong answer. My 92 SEFI LX did the same thing right before I lost every gear short of 4th?!! don't ask me, I'm not a mechanic, but if you have the 1.9 EFI HO Motor, you have the same Tranny as mine. Trust me, I've looked it up. I'd say it'sa faulty Tranny, Sorry.

Thank you

My engine is the 1.8. As far as *I* can tell the clutch is engaging perfectly (considering I just put a new one in 3 weeks ago). Since my first post it has now clunked going into reverse. I fear your diagnosis may be correct, but of course, am hoping for the best.
I can't help but wonder if the clutch work 3 weeks ago may have been a precurser for this problem.