1992 300zx vibration

Is it a fast (engine, transmission, driveshafts) or slow (wheel, tire, hubs, brake disks) vibration?

Is it a body vibration (as exhaust touching the body) or a powertrain (suspension) vibration?

From your description, assuming that the vibration is there only at 40 m.p.h, I assume it is a slow/suspension vibration.

Have you measured the run-out of the wheels, hubs, disks?

What about tires, have you checked them for flat spots or band separati> Hi This is my first post....

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.

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.

Thanks for the help , I'll start saving for a new propshaft!

Cheers