My 75 911S was sitting for past 6 years. I got it running after replacing , fuel pump, points, spark plug wires, condenser, distributor, drained the gas, fuel filter. Got it started, 1st time I drove it no problem shifting into reverse. All forward gears work fine. 2nd time I drove it I had a hard time finding reverse gear but finally went into reverse. Now when I try and put it into reverse it only shifts to 4th gear. Any suggestions would be appreciated. Thanks

 

I'd look at the coupler bushings first-if the're original it wouldn't be a surprise if they are crumbling.

 

I would check coupler adjustment first (loosen it and then re-adjust). Or there could be something wrong with the shifter itself. There is a lock that prevents shifting from fifth to reverese, maybe it is not working properly? Removing the shifter, checking that everything is ok, cleaning and greasing it would be a good idea..