WOOM, WOOM, noise from rear-end.

[deuce-Z]

I recently acquired a '78 280Z and am in the process of restoring it, everything works well and is in decent shape except for the rear-end.

It had a nasty CLUNK when shifting gears and makes a WOOM-WOOM-WOOM noise when you get the speed up to about 30mph and up. Well I checked the differential and sure enough it was shot with about a half turn of play on the input yoke. I found a nice tight used one locally and swapped out the old diff.

That cured the CLUNK noise but it still has the WOOM-WOOM noise. I took the rear brakes apart no sign of problems, and I took the rear hubs apart to check the bearings, everything was great and fresh grease didn't stop the noise. I did notice that the left axle was difficult to pry out and the right came out easily. The noise "seems" to be coming from the left but it's difficult to tell for certain.

Should I try a new axle shaft on the left or has someone else encountered this problem? My other suspect is the strut any thoughts would be greatly appreciated.

[=Enigma=]

Welcome to the site. It's often difficult tell exactly where a noise is coming from while driving in the car. Does it get louder when you are making a turn? If not, is the noise still present when coasting in neutral, or just when you're in gear? If the latter, does it happen when you're accelerating or decelerating? Just trying to narrow the focus.

[deuce-Z]

Welcome to the site. It's often difficult tell exactly where a noise is coming from while driving in the car. Does it get louder when you are making a turn? If not, is the noise still present when coasting in neutral, or just when you're in gear? If the latter, does it happen when you're accelerating or decelerating? Just trying to narrow the focus.

It only does it at road speeds [30+ mph] and it does seem to get louder when I'm going around a left hand curve. It does it in neutral or any gear and does not seem to be effected by acceleration or coasting. It doesn't always do it either sometimes I can go a day or two without hearing it and other times it's constant when it gets up to speed.

It sort of sounds like a tire or something rubbing, but I've thoroughly checked for clearance and for any shiny spots on the rear-end components. I've even tried putting it on the lift and running the wheels up to speed, but can only get the noise when it's on the road.

I've visually inspected for any bent or damaged parts and everything looks just fine. Like I say the only thing I've noticed is the left axle has to be pried out and the right comes out easily. One other thing I noticed is that there is some Bondo on the left door and quarter panel, which leads me to suspect that it was hit on the left, however there is no noticeable damage to any of the rear-end components and the body does not looked tweaked from a bad wreck just some sheetmetal work on the left side.

I've always considered myself a fairly competent mechanic but this one is really throwing me for a loop. It also looks as though someone else tried to figure it out as well, when I was checking the bearings the left axle-nut had been removed previously but the right side nut had never been touched. It doesn't seem serious but it as me wondering if this might have caused the differential to go out?

[Nissanman]

From what you are describing, to me it sounds like bearing noise.

Also, your description of damage may indicate that at one stage it hit something [curb?] on one corner.

That may be enough to have bent the stub axle, maybe the wheel flange or stressed the bearings.

Perhaps use a tape to determine if LHS wheel flange is same "D" from centreline as RHS wheel flange.

Have you spun the rear wheel and checked it for runout?

However, something a bit cheaper and easier to try would be changing the rear tyres to another set [the fronts perhaps].

All a tyre needs is a small blemish and it will generate harmonics at speed:rolleyes:

Anyhoo, can't hurt to eliminate tyre noise.

My sons' 240Z had a bent wheel flange on the back LHS which we didn't know about until we did a disc brake conversion.

It was way out of whack, needed a replacement stub axle:ermm:

[datsunrides]

I have had similar issues to your and one time it was a bad driveshaft(ujoints and balance) creating some harmonics that transmit thru the body, another was a bad trans mount creating the same "symptom". I also had a bad tire cause a similar problem. The tire drove me nuts because it was an internal tread separation, the outside looked fine until one day a bubble formed and exposed the problem. Some food for thought.

Mark

[deuce-Z]

Thanks for the replies!

I've got some spare axles that came with the differential. My next step is going to be swapping out the left axle shaft.

My first thought was bearings too, but I've already checked them and couldn't find anything obvious. I hadn't considered the tire but now that you mention it that is a very distinct possiblity. While I've got it in the air I'll try swapping around the wheels.

Thanks guys, I'll let you know what happens.

[=Enigma=]

Keep in mind that the rear bearings can easily be damaged when removing them. If they don't come out real easy, odds are that some damage occurred while removing them and they should be replaced. Some people say they should never be re-used but I'm not sure that's entirely true. The OEM manual covers removal/service/replacement of existing bearings so......

That said, this does sound like a bearing problem on the left side, but the suggestion about a bent stub is also a good one, especially if the left rear side was hit, or if the P.O. tried to hammer out the stub with a sledge hammer some time in the past. If it's not obvious by looking at it, you may have to take the stub to a machinist who can throw it on a lathe or some other device and measure the runout.

[deuce-Z]

Well I swapped out the left axle and switched around the tires. This has quieted down the noise considerably but not eliminated it entirely. I hear it occasionally but not as frequently and it is much quieter.

The axle I removed had been swapped out before and was marked with a junkyard crayon '82 280ZX. It appeared OK but the other axle fit in place much easier than the ZX. I laid them side by side and they looked identical but for some reason the ZX axle fit in there tighter.

I suspect there maybe bearing damage or wear but since the noise has quieted, I'm going to just try it for awhile and see what happens.

Thanks for the help.

[=Enigma=]

The compressed length of the 280ZX half shafts are a bit longer, which may have caused binding in the suspension as well as excessive pressure on the inner wheel bearing and/or the carrier bearings in the diff. Swapping in a half shaft with a shorter compressed length may have taken some of the load of the bearings which is probably why things are a bit quieter, but the damage is done. I say drive it until the noise gets unbearable or you have the time/money to replace the damaged parts.

See some controversy on the 240, 260, 280 shafts here:http://www.betamotorsports.com/benchracing/R200handling.html

[deuce-Z]

Thanks for the link Enigma, interesting read.

I took her for a ride up to a friends house in the mountains this evening. It's a 20 mile ride one-way with some good grades and curves, so I was able to wring her out good. The noise was nearly gone except for an occasional WOOM-WOOM which seemed most noticable when decelerating.

I hadn't really thought about it before but there was a slight vibration when the noise got loud. Now there's no vibration even when I hear the noise, of course it's not as loud either.

I agree it's almost certain there's bearing damage and I won't feel right until I've changed them. The only thing that bothers me now is if I go through all that work and the noise is still there!

I'll wind up doing it of course, but at least now it's not a top priority, I can just turn up the radio now.