Yep! Just wait till the VTC's start leaking oil and the tensioners all need
to be replaced..

That is what the driveshafts do. A tire will be a much slower vibration,
about 1/3-1/4 the frequency of the driveshaft.

Nope. In 4th gear it's "straight through" i.e. the input shaft is coupled to
the output shaft and I bet it does it in 4th and 5th gear.

Like I said about 80% of the reman driveshafts we have installed (at the
customers request) have had a vibration and I've had 2 dealer shafts that
were bad right out of the box! Also make SURE the thick spacer washers for
the center support bearing are between the bearing support and the body.
I've seen this mistake too.

Someone told me I'd need deep pockets with this car!

The vibration is a fast vibration starting at 40 and disappearing at
about 70

Steve T, before I replace the driveshaft , is there any chance it could
be the transmission?
The synchros have seen better days and gear selection (especially
reverse) is an art!

It's the driveshaft.

The only -fix- is a new driveshaft from nissan. Almost every "repaired"
driveshaft we've tried vibrated as bad or worse than they did before the
repairs. These cars are ULTRA sensitive to a less than perfect driveshaft,
I've even had new from nissan ones that weren't smooth and had to be
re-replaced before the vibration was gone.

Hi This is my first post....
I recently purchased a 1992 300zx TT.
Great car but for the vibration at 40+ mph.
The vibration is felt through the seat rather than the steering wheel
and is at its worst from cold.

I've replaced the propshaft centre bearing and had the universal joints
repaired.
The prop has been balanced and the gerbox mount replaced.

It still vibrates, I've tried different wheels, no joy.
I'm going to try 4 wheel alignment next but , assuming this doesn't
work

does anyone have any ideas?

Thanks