GM Synchromesh Friction Modified. Get the AC Delco White bottle and save some cash.

 

As the others have suggested, I would try changing the transmission fluid, since that's an inexpensive attempt to find a solution. I would recommend going to the local dealership and buying two quarts of Honda MTF, P/N 08798-9031. It is less than $6 a quart and you only need two since it holds 1.6 quarts. Do I think it will work? I doubt it but for $12 it's worth a try. Do a search, there's a thread that shows each step for doing the fluid change. Most likely, your transmission needs a rebuild, since 5th gear is not typically a problem gear. Good luck. Otherwise, the only thing you can do is baby it when puttting into 5th gear.

 

All my gears work except 6th, I can't get it to engage. Has anybody fixed it on their own?

 

I have a question. Does shifting the car with the clutch pushed in when it is parked and the engine is off do any harm to the syncros or transmission? Im curious about this because at the dealership people are sitting in the car and shifting and a saleswoman said not to shift when the engine is off because it is hard on the syncros. Thanks.

 

It's not a good idea, but there's really no harm being done. But the gear collar are designed to go in and out while moving.

One bad shift out on the road does 50 times the wear.