i posted this on g35driver, thought i have it here since our 6mt trannies are the same......

driving around one day and bam.....5th gear will not engage at all......so i put in neutrual and try again.....nope.....all other gears are ok, except for the occasional 1st and 1-2 notchiness......car is at dealer.......anyone had this happen before? what happened? searched, but nothing on about 5th shows up...
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04 6mt blk sedan: 05 Z suspension, Ztube, Zmiddy, Z track 18" wheels w/dunlops 245/24/18 all around + bolt-ons good for 257whp and 245tq on dynapak w/exhaust leak .......S/T in the planning stages. The few, the proud, the 6mt sedans

 

Don't know the exact particulars of what went wrong, but sounds like it's time for a new tranny. Your warranty will cover it, assuming your car is still within warranty.

 

have about 55k, so warranty is still valid...........just waiting for call from dealer and hoping to hear, "we're replacing your tranny".......that will make my day for sure.

 

does 5th Rev like neutral? i had the same exact problem.. but it was 5th and 6th.. got my tranny replaced under warranty

 

Check the shifter guide plate... It may be something as simple as that...

If you have an aftermarket shifter of some kind, I have seen bushings on them wear out and not allow to shift into 5/6 or R...

 

This happened to me. Dealer replaced the tranny. It's a pain. Sorry.

 

Getting a new tranny......priceless.