I'm getting ready to fix some problems a had before I put the gta up last fall. Namely no 5th or 6th gear. 1st though 4th works fine as does reverse but if you go to 5th or 6th the shifter will stay in place but it has a high pitched whine/grinding sound and no gear. From the manual and exploded diagrams it looks like the 5th/6th gear shift arn is held in place on the rail by a pair or c clips. could one or both broke or come off? Or am I looking at a rebuild?

 

If u haven't started yet..
The good news is 5,6,R are located on the backhalf of the trans so you should only have to remove the tailhousing to service those gears. I would tear it all down though. Not that much more work.