(6-speed MT) On occasion, ONLY after driving for 20+ minutes, it becomes more and more difficult to shift gears, particularly Reverse and going into 1st from neutral. I have to re-pump the clutch twice, sometimes more until it becomes unstuck, while almost forcing the shifter. It is usually followed by a loud noise from beneath the car (transmission?) when the gear is finally shifted.. Other than that, my car runs well and fine 75% of the time.
This also never happens from a cold start. Also, the problem goes away once my car has been off for at least an hour.

What could be the issue here? Clutch going bad? Synchros? Tranny fluid? Clutch / Differential fluid? or worst case scenario... transmission going bad? Something else?

This is stressing me out.

I just bought this car used a few days ago and the previous owner did warn me about it, but he was clueless as to what causes it. Also, it has a short-throw shifter if that helps.

 

What year is your car..? How many miles are on it would also help...?

 

2003 w/ 133k miles.

 

If I remember correctly 03 models with 6mt were notorious for synchros going bad..

 

Easy to tell if it is the clutch which is my guess (no a worn clutch will not do this but another issue will). Does the problem persist if the car is NOT running? If so, sounds like either a clutch pressure plate issue or a release mechanism issue. Aftermarket clutch? How many miles? Could be what just happened to me... Pressure plate bolts came loose.

 

So we got the clutch slave cylinder replaced in addition to new fluid, BUT the problem still returns after the car has been running for 20+ mins.

Going to take it back to the shop tomorrow for a possible master cylinder replacement.

 

Do you still have the OEM rubbed hose near the slave?

 

I don't know. Could a bad hose cause the problem? I'll have the mechanic check that part as well.

 

When that rubber warms up it becomes maleable. It causes your symptoms. Get a stainless one from z1 or concept z

 

could be old trans fluid heating up and thinning out.