1990 ZX Vibration only under acceleration - chked u-jionts
 

I have a 1990 300ZX 2+2 NA

My vibration is only under accelleration - not when the car is in N rolling down a hill - so I know it's not wheel/alginment realated. Any help would be appreciated. I did read the many posts related to possible u-joints & 1pc drive shafts. I was hoping it was that, but.....

I just went under the car to see if there was play in the u-joints, and they seemed very tight (well, the rear piece of the shaft that I could get my hands on - without removing the exhaust). I also jacked up the rear of the car with both rear wheels off the grould (car in N and parking brake off) and there was very little play at the rear wheels - maybe a 1/4 of an inch. Any help would be appreciated. Thanks in advance.

5 speed or auto? If it's a 5 speed, it could be clutch chatter... May also be the carrier bearing which is very common problem and a little harder to check than the u-joints. Rod.

vibrations...
 

If you end up having to do your U-joints, I would suggest upgrading to a 1-pc drive shaft. The original design was created only to reduce the road noise but I would upgrade rather than fork out aton on a carrier bearing. Fix em all at once.

COZ has a ton. Reasonable price too.

Vibration - sorry, it is an Automatic
 

Thanks - sorry, it is an Automatic. Where is the carrier bearing located? Is that in the rear end housing or part of the driveshift (as the reponse to the thread is hinting it)?

you need to read this...

http://300zx.co.uk/cgi-bin/manual.cgi

You may also want to check the alignment of the tailshaft of the transmission. But most likely you have an issue with the driveshaft center carrier bearing. The only other thing that crosses my mind is a serious indication of a transmission problem. How about the flywheel? Had it checked? Slipping? Clunking? Any leaks? Have you had the fluids changed?

Is the vibration in the steering wheel? in the seat of your pants? or rearward?

A common thumping / shaking / vibration from the rear, under acceleration is from worn out rear shocks. The d/s is a higher frequency vibration that you feel in your butt.

Thanks - will gather more info
 

Thanks for all the input so far. I will gather more info on the vibration this weekend. I believe it seems to be centered around the middile of car and is more noticable starting around 45 or so mph and up. And I don't believe the steering wheel really shakes much either. It is an automatic btw. Like I said, I'll get back on with more info to aid troubleshooting - thanks again !