Hi everyone, I have an ’84 car with a clunking (donk donk donk…) noise coming from the passenger rear tire area that I’m looking for some help diagnosing. It seems to change consistently with the speed of the car, so I’m thinking it’s coming from somewhere in the transmission - axle - hub assembly. It’s only noticeable at low speed (<20mph), especially while decelerating. It also tends to happen going through right hand corners.

The passenger rear wheel had some play up and down, seemingly from the rear wheel bearings, so I changed those on both sides. The outer passenger bearing literally fell out when I pulled the stub axle out. I also replaced all the spacers and seals. Immediately after changing them, the passenger side wheel had no play, and the driver’s side had a tiny bit (having previously had none). The noise seemed to go away for a few days, but then it came back, although it does seem to be a little less loud. About two weeks after I changed the bearings I went back in and re-torqued the axle nuts and they both moved 1/6th of a turn farther, but that had no effect on the noise.


I also looked for play throughout the driveline:

If I pull out on the back edge of the bottom of the wheel, or push up on the bottom of the wheel, some movement occurs. Not a ton, but it’s definitely perceptible.

The hub CV is rock solid, with no detectable play. The trans CV has a few mm of play in and out of the transaxle, and about 1mm of play vertically and front to back.

The axle probably has about 3cm of play in and out of the CVs.

That’s for the passenger side, the driver’s side has similar, but less play in the wheel and the transaxle CV. The axle and hub CV are the same as the driver’s side. With the car in gear, with one side lifted, each wheel can be rotated probably about 10-15 degrees.



I also changed the transaxle oil for the first time since I’ve had the car (~8 years), and what came out had a pretty significant amount of brass flake in it, but the transmission generally works well.

At this point I’m thinking that the stub axles are worn, even though they looked good when I did the bearings. I can’t say that I gave them too thorough an inspection. From what I understand the rear wheels should have zero play with fresh bearings. I’m also considering flipping the axles around to see if that gets rid of the noise, which I guess would indicate a worn CV joint.

Does anyone have any suggestions or ideas as to what I can do to diagnose/eliminate the noise?

 

I highly suspect axles and the idea of switching sides is a good one.

Some 944's can use VW Vanagon CV joints (matched to the existing 944 axle shaft). They only work if your axle shaft is 33-spline. I think its only for late model 944s but not 100% sure-you should check your shaft spline count before ordering

FWIW I am running these in my 89 S2 and theyve been great (autox'd a number of times with no issue). PO had installed cheap Rock Auto axles which ended up breaking on me after I bought the car, and with the price of OEM, these ended up being great value and quality.

 

I agree with swapping the cv axles side to side to help determine if the left axle is making the noise. The axles will cause a rattle and should be cleaned and checked for excessive wear and repacked with the appropriate cv axle grease.

Check to make sure the rear brakes are secure and that a pad's friction material has not separated from the metal portion. A loose caliper or pad will make noise at speed.

Can you duplicate the sound with the rear jacked up on jack stands? Have you checked the rear shocks? I had an 84 944 that had a simar issue, though it was more of a rattle at lower speeds and it ended up being a bad rear shock. The car had a great ride but made a rattling sound at lower apeeds. Is your noise a rotational noise?

 

I flipped the passenger axle end over end (hub to trans and vice-versa) last weekend, and I think it would have been wiser to actually swap them side to side like you guys suggested. I think the idea of changing the load on the CVs still works with how I did it, but the noise is still there (maybe a little quieter) and seems less easy to pinpoint location-wise. At times it sounds close to the hub, and at others it sounds like it's closer to the transmission. Before it was easier to define as being at the hub. Maybe both CVs are bad and need changing? Would there be any advantage to buying entirely new axles rather than just changing the CVs?

I replaced the rear brake pads and rotors last weekend as well, and the noise is still there, so I'm thinking it's not the brakes. Everything seems to be in good order in that regard. I can't replicate the noise by manually spinning the axle, but I haven't tried running the car on stands. I might have to try that. Although the noise is much more apparent off-power than on.

The rear shock idea is interesting because both of my rear shocks have definitely leaked oil, the passenger worse than the driver's side. The car still rides fine though, like yours did mazdaverx7. I was planning to change them in future once I had all the mechanical maladies fixed, but I might have to do them sooner rather than later. The noise does seem to be rotational though, its frequency is proportional to the car's speed.

I suppose my first order of business will be to swap the axles side to side; do you guys have a suggestion as far as best CV orientation? Bolt the joint that was attached to the hub on one side to the hub on the other, or swap it to the transaxle?

 

Yes, please swap axles from side to side and see if the sound switches sides. If it does not switch sides there are then other things to investigate. (wheel bearings, differential, trans mount, parking brake for instance)

 

As a note, shocks that leak oil are weak and should be replaced. I would replace them and if it solves the noise issue then awesome and if not at least you've eliminated one potential possibility and will have a better ride. If its rotational like you describe then it likely will not solve the issue. I remember experiencing a steady rattle from the rear, even on surfaces that did not seem bumpy. I first though it may have been rotational noise but after listening carefully I felt as though it was not proportional to the speed, but more of a steady noise.

 

Sounds like axle

 

I have now swapped the axles side to side, and changed the rear shocks to no avail. The noise is still coming from the rear passenger side, and I can't be 100% certain, but it sounds much closer to the hub than the transmission. Should my next order of business be to dial the parking brake shoes all the way in, just to eliminate the possibility that noise is from them rubbing?

Can anyone confirm whether or not a bit of play in new rear wheel bearings is normal? I'm guessing it's not.

One thing I've noticed lately is that if I don't match revs 100% perfectly on downshifts into 2nd, the drivetrain has a bit of shuddering/skipping action. Might this indicate that the problem is in the transmission?

Thanks for the help everyone.

 

Rubber bushing in clutch or ring and pinion gear in transmission

 

If you decide to go with completely new axle shafts like I did in my ‘83, then look for axles out of a Super Beetle or a VW thing. I found Empi ones at JBugs.com. They came out of South America and went right in. Slick. Not Chinese which made a difference to me. BTW before you totally tear down the axle bearings again, put a dial indicator on the shaft and check out the roundness of the shaft/ bearings. Just a thought. HTH some.

 

No I dont think you should have any play in your rear wheel bearings, and since the sound did not change sides when switching axles, I would highly suspect rear wheel bearing as the cause.

 

It could, does it grind when putting it into gear or just shutter/skip when releasing the clutch. It could also be an issue with the clutch as well.

 

I do suspect that both the clutch and transmission are fairly worn. I've had the car for 8 years and have not replaced the clutch, and when I shift gears I do meet resistance on occasion. The shuddering/skipping only happens on an imperfect rev match though.

As far as the wheel bearings go, I may have to give the stub axles a check with a dial indicator as suggested by Tiger. When I replaced the bearings they came out and went in fairly easily, but I did need to use a drift to remove all but the outer passenger bearing. That one just fell out. The stub axles also took a good bit of force to get in. If the stub axle doesn't have runout, would it be reasonable to assume that the bearing seat in the trailing arm is worn out? That seems unlikely to me, but I guess it's possible.

 

I’m following this closely. My 85.1 has a knocking sound from the rear passenger side when turning left in 15-20mph range (neighborhood driving). It will go away after I straighten out. I’ve been thinking wheel b’s but I haven’t investigated yet. It’s just on my never ending list of things to fix.

 

Probably not stub axle wheel bearing because only noise in turning. More likely one of the U-joints of the half shaft on the passenger side, turning causes half shaft U-Joints to change angular orientation, binding occurs if U-joints has woren internals.