Transmission or differential problem on a 1972 240z with 160000 miles on it, car has sat for 8 years, bought it 4 months ago, got it running, doing about 40 miles per hour and grinding noise starting coming from the rear passenger side differential area. Noise only when I try to excellerate but all the gears seem to work and shift ok. Before I start to get into it, just wanted to get an idea what to look for or what the problem could be. Have not added or changed any fluids in trans or differential. I am wanting to fix as much as I can myself and keep original.

Bearings.

I was thinking about trying to replace my bearings in my rear end, but after reviewing the FSM, I do not think its a DIY type of job. Many special tools needed both off the shelf and Datsun factory special tools. Not sure as I am pretty sure I have a rear bearing on my passenger side of the diff that needs some removing and replacing. I think I may just try to replace the whole thing. I just have to find one that is in better shape than mine.

I'd suspect wheel bearings before diff bearings. If it is diff bearings, the diffs don't have serial numbers, so any 3.36:1 R180 out of a 240Z is going to be just like any other.

Wheel bearings generally react to side to side thrust. So if you swerve back and forth you should hear the noise stop or change on a wheel bearing. The diff is in the center, so I doubt you'd be able to tell passenger's side carrier bearing from a driver's side carrier bearing.

Could it be simply one of the u-joints on the halfshafts?

Could it be simply one of the u-joints on the halfshafts?

u-joint symptoms are usually a clunk sound, grinding noise seems to be brakes or bearings, my vote is bearings.

I'd suspect wheel bearings before diff bearings. If it is diff bearings, the diffs don't have serial numbers, so any 3.36:1 R180 out of a 240Z is going to be just like any other.

Wheel bearings generally react to side to side thrust. So if you swerve back and forth you should hear the noise stop or change on a wheel bearing. The diff is in the center, so I doubt you'd be able to tell passenger's side carrier bearing from a driver's side carrier bearing.

I agree completely. I say that because I have been thru the wheel bearing thing with my 1972, as well as several other Z Car related issues's. And sitting for so long did not help anything on your car as well. And I say this because mine sat in a garage for 7 1/2 years. One of the first things I did was get rid of the 3.36 R180 and put in a 3.54 R200.What a difference. Got the R200 for $150.00. Now 6 years later and many hours of tinkering and fixing it runs perfectly. Drive him just about every day and we both love it. Now all I have to do is get a little extra cash together so he can get painted.

Edited January 9, 201015 yr by barth4567

My grinding noise in the back was from bad rear brakes when I got my car after it had less than 5000 miles between 1983 and 2008. After a rear brake rebuild and new master it was fine. Going to have to replace the u-joints some day, its on the list.

Start you diagnosis and fix from the simple and cheap end of the scale. Remove the wheels, tires, and brake drums and start inspecting there - as suggested above.

Man everybody is right it could be anything. Some times when some one works on the brakes they bent the back plate so the drumm drags around it thus making a grainding sound. also the bearings can be on the differential or the ones on the hub.

Hey everyone, I drained the differential fluid and refilled. That was the problem, very little drained out and now the noise is gone. All I can say is thanks to everyone, I feel good to be a member of the Classic Zcar club.