I own an '02 GT Mustang, 4.6L, 5-Speed. I have 42,000 on her and I have a problem. When I shift up from 2nd to 3rd It grindes. The same when I come down from 4th to 3rd. I know that it is a syncronizer issue. I have had it in 2 shops and I have gotten estimates from$1100 to $1700 to replace 2 syncronizers. Would I come out better replacing the syncronizers or rebuilding the entire thing, or replacing it with a new, after market??  The car is stock, not driven hard at all. I live in Lower Alabama. Can anyone give me direction ???

Thank you 

The rebuild option is costly because of some of the problems with rebuilding manual transmissions.

The options I'd recommend is A) Getting a good tranny from a salvage yard, or B) Upgrade to an aftermarket tranny.

If two of the synchros are going, odds are the others aren't far behind, so just replacing the bad synchros would only be a temporary fix. If you hunt around you might be able to find a used Tremec to install in your car.