For some reason when I'm driving around town for hours I have no problems at all but when i do a bit of a spirited drive and the transmission gets a bit heated up I can not engage the 1st and 2nd gears . Either they are impossible to shift into or they grind .

by the way I have a 1980 928s with 5 speed manual .

Does this mean I need a rebuild ? Other than not being able to engage 1st and 2nd ( unless I shhift 3,2,1) there are no problems at all . I even had the fluids serviced to see if that would fix it .

 

Make sure the double disk clutch in your car is properly adjusted and working correctly first. If you're sure that's okay, there's a good chance that you need new synchros. The synchros in the early 928 manual transmissions are a well known problem spot.

 

Just put new syncros in my 84 911. 1st and 2nd synchros are on the same rod. Did you hear any popping noise. When mine went there was a popping noise then I couldn't engage 2nd.
It is bad news if that is the case, mine cost me $2300 to fix.