Do you have a R180 or a R200 3.9 diff?

This is an R180 that I got from eBay last year. It was inspected and new seals were installed by Eiji at Datsun Spirit.

I had this problem also. After replacing the drive shaft u joints, it was still there. On a whim, I rotated the drive shaft 180 degrees on the rear flange to differential. The vibration went away. Maybe I was just lucky, but someone, at some point had misaligned the drive shaft. Good luck. Sometimes the most simple answer is the fix.

Coastal Man,

Tell me a little more about your symptoms. Exactly what do I do with the driveshaft; I'm not sure that I completely understand.

Peter

The drive shaft is held by 4 bolts - if you remove the bolts - rotate the driveshft 180 degrees and rebolt. It will re-align the drive shaft. Or - take it to a balance shop and have it balanced.

You could still have a new u-joint hung up in a bind.

Thanks Mitchell. This is a new driveshaft that I got from MSA but it won't hurt to check.

Found this tonight looking for other info:

This may not apply to your case but it could apply to somebody else researching this thread:

GROWLING FROM REAR AROUND 70 MPH

This is usually due to a worn out rear joint on the driveshaft. Go under and twist the driveshaft joint where it bolts to the differential. There should be no slight clicking or play, but after 30+ years it's gotta go sometime. Unfortunately, the joints on 280Z/ZX driveshafts aren't replaceable. Nissan made them cheaply by stamping the joints in, so there's no way to remove and replace the circips and joints. The junkyard is a good place to get a replacement but you're still stuck with a very used part.

The solution is to have a custom driveshaft made, about $300 dollars. Either look in the yellow pages and find a driveshaft fabrication shop, or contact Powertrain Industries. These guys are Nissan specialists and made me a custom driveshaft which was very high quality.

Mitchell stated just what I did with the rear end of the drive shaft. I was getting a vibration around 70 mph. Not terrible, but not what you want for long trips. Rotating the drive shaft along with new u joints (which were put on first, but did not make the vibration go away) smoothed out 90 percent of the vibration. I will have the drive shaft balanced at some point, but it is not anything that needs to be done right now.

Charlie