Hey, hopefully you can help me... I've been looking at this 1990 300ZX with about 78000 miles. When I took it for a test drive, it felt 100% top notch until 35mph, where it proceeded to get a vibration that felt drivers side rear.. The car has brand new tires on it, but I'll have the person have the alignment checked tomorrow. I read something about a driveshaft wobble, when the U-joints or center support bearing are going bad on the driveshaft.. Has anyone had this problem before? How did you fix it? How much did it cost you? Is it a BIG problem, would it have messed up anything else too which also would need to be fixed? Should I be looking for a different car?

Thanks so much, Robb

I think its age that sags or perishes the rubber on the centre bearing support. You should find that the vibe is worse when cold but once that exhaust heat hits it it seems to get better. I got under and looked at mine to find the bearing and shaft virtually sitting on the support. Tried jacking the prop shaft up carefully near to the support and you can see once the rubber is streched a bit that it is all perished and tore. Mines a 92. Just tried a bodge to see the effect and slipped in a couple of strips of that thick clear polythene about 5mm thick (you get in factory door curtains that fork lift trucks barge thru) You have to do that when the shaft is jacked up. Guess any rubber strip would do under the bearing and above the support. You drop the shaft onto the strips and voila it seems to sit more central in the surround on the bodged mount.

Result was that the vibe has gone and the car feels very smooth in the 35 - 50 range where it was worst. Still slight vibe apparent at higher speed though.

Gonna fit a new centre bearing asap - looks about £130-£140 cost to buy once the VAT is in.

Willie

 

PS had my Z 18 months and it has been getting slowly steadily worse. If thats all thats wrong then its not too bad. If the UJs are good. Otherwise best part of a grand from Nissan for a new propshaft or £200-300 to have the joints rebuilt at a machine shop specialist. UJs should be OK unless it was owned before by a donutmeister!!

Good to know, thanks.. is there any way I could determine it was the driveshaft, rather than another problem. I read putting the car in neutral during the vibrations would cause it to cease, being a quick effective way to find out if it is that problem. But that wouldnt stop the driveshaft from spinning would it? it rather would take the engine out of the equation. Ack, so confused... Is the repacking of the bearings method of fixing this problem as longterm as getting the whole assembly replaced by nissan. (which I hear is insanely pricey) I just need to figure out how much it would cost to get this car in prime condition. Thanks for the help, Robb

Get it up on a ramp and take a looksee. You can see the mount from the rear. Its just inside the heat shield section.

Putting it in neutral does nothing as the propshaft still spins. The vibration must come from a combination of the misalignment of both halves of the prop causing a small acceleration and deceleration of the 2nd half of the shaft rotation speed every half revolution. the frequency must be such that there is a resonance between 35-50 and the stuffed rubber flexy mount having sagged so much means the bearing is on the bones of its arse so to speak then transmitting said vibration right through the floor near where you sit.

Incidentally a colleague consulted with a supplier of butryl nitrile (dont know if the spelling is right or even if its the same rubber) rubber compounds for a product my company thought could last 30 years. The rubber supplier then said it lost its properties within about 8 - 10 years depending on ozone UV heat etc. I guess most 8 - 10 year old Zs need the centre bearing changed soon i.e now now along with the rear gearbox mount. Nissan is probably already stocking up. My rear transmission mount looked a bit saggy too but it was easy to jack up and insert some additional rubber strip into the gap in the mount it to raise the box it back to where it should be.

Hope this helps

Willie

I BOUGHT A 300ZX FROM NEW IN 1993 AND HAD ALL SORTS OF VIBRATION FROM THE BACK END USUALLY AROUND 30 -40 MPH. IT WAS SIMPLY RESONANCE CAUSED BY THE TYRES BADLY BALANCED. START WITH THE EASY THINGS FIRST. FROM THEN ON I MARKED THE STUD TO THE WHEEL TO ENSURE THAT THE WHEEL ALWAYS WENT BACK IN THE SAME PLACE. AFTER FIRST HAVING THE WHEELS BALANCED BY A COMPETENT COMPANY. ALSO CHEAP TYRES ARE A WASTE OF TIME AND COULD CAUSE THIS PROBLEM. GOOD LUCK.

i have exactly the same problem with my 92 uk zed. it vibrates mostly at 40mph when the car is cold and then goes completely after about 10min of driving. guess i need to get that centre bearing changed by the sounds of things.

 

cheers

 

Steve