Interesting shifting problem
 

Hi,
76 targa 915 transmission.
I have sweptco oil since last year.

What I’ve noticed recently is that on cold the car shifts fine no problem but once i drive it and the engine and transmission oil warm up (plus it’s warm outside) I noticed it grinds in first gear and reverse is really bad.
Clutch cable is new since last year.

What would cause grinding when oil is warm?

Thank you

grinding in reverse suggests that the clutch is not fully disengaging the transmission from the engine (as reverse lacks synchros and it sounds like it's still spinning) -- will reverse engage smoothly if you first shift into second gear and then immediately into reverse (this should stop the gears from spinning if the clutch is fully releasing)?

Sounds like you may need a clutch adjustment.

I will try that maybe the cable stretched since last year and I need to adjust.
Thank you

check oil level
could be that the thicker (cold) oil is helping the syncors not slip vs once it warms up the oil gets more "slippery". kind of why synthetic oil in some gear boxes is not a good idea.

not a tranny guy and maybe I did not explain it properly.

one if the "rules" for Porsche gear boxes is 2nd before 1st or reverse. more so with the older 901s