The synchros are crap in 5th and 6th. I had my tranny completely replaced under warranty about 5k miles ago. I really think it's either you get good ones or you don't. Nissan really has a knack of having issues like this with their cars.
No issues with the new tranny but it only has 5k miles on it. Oh and I added 250hp/tq since then so I wouldn't blame the tranny if it craps out on me.
