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At last, my car ('83 944) has presented me with a problem.
I was driving along back roads when a knocking sound began, and got louder for a bit. It seemed to be coming from the rear left corner of the car, and was only noticeable when in gear. It was more prominent under acceleration, and died off when cruising above 40-45mph. After 4-6 miles of driving, the sound faded. The sound seemed to match the rotation of the wheel/axle/speed of the car, rather than engine speed. The whole time, the ride didn't feel irregularly bumpy, or anything.
Thoughts anyone? Would bad wheel bearings be so sensitive to being in gear, or be likely to make noises that come and go? Perhaps the axle is bad? The transmission felt fine, synchros in all gears operating as they should, etc. There has been a slow leak, and I just bought fluid to refill if necessary, but if it were the gearbox somehow I'd expect to know...
I thought I'd jot this down before getting messy and possibly changing my perception of what the issue might be by poking around and noticing things that might be out of place.
Side note: I have surprisingly mixed feelings about this. Obviously I like it when a car works, but I've been waiting for the day when something goes wrong, and now that it has, there's no suspense or wondering what will fail. Plus, it gives me an opportunity to get to work on and learn the car better.
Jacked up the car, and the left rear brake catches the wheel at the same point in rotation. During light braking, I've noticed before that one of the rotors on the left side of the car seems to be warped, and I get a small amount of shudder, but it felt more like the front. (I tested the front wheel while I had the car up, and the brake pads seem to rub on the rotors a small amount but I can turn it by hand and it goes through a couple rotations before stopping, so it doesn't seem plausible to me that it would be the cause.) The noise didn't feel much like the brake grabbing, though... Any thoughts on this?
The rear left wheel doesn't seem to have the side to side play that my right front wheel, which needs to have the bearings tightened, does. I can turn both axles near the transmission and hold the wheels still and there's a bit of movement, but I have no experience working on these, so that could very well be normal.
Does anyone have ideas of what else to check? (In case it isn't obvious, I'm new to working on cars, so any input, no matter how basic, would be greatly appreciated!)
I would get the car in the air and yank on the cv chafts, the wheel and the suspension links including the sway bar. I'd also check to see that the lugs are torqued to spec. I strongly suspect there is play in there somewhere that is creating some sort of osculation.
I would like to know more about that rear wheel bearing you mentioned. I should be a giant needle bearing arrangement so it shouldn't have any play. So far I would say that might be your culprit but I agree it shouldn't be that loud
I looked more carefully at the CV joints, and there's a lot of build up on one side, as if the car sat for months (which I have reason to believe it did) leaking grease slowly. Besides that there's nothing strongly indicating to me that it's the problem, but since it seems to be a common cause of this sort of isolated knock, I think I'll go ahead and pull them out, clean them, inspect them, and re-grease. If the knock continues, than I'll concentrate my efforts elsewhere.
The rear rotor being warped has been driving me crazy anyway, so I think I'll suck it up and order new ones for the back (the front are new), and give the wheel bearings a good going over when I'm in there. I'll have to do the same with the front anyway so it'll be a good opportunity to get acquainted.
I have no idea when the wheels were last removed, but the rear tires are getting low on tread and were a bit deflated, so re-checking the torque is probably a very good idea.
Lots of work to do! On the plus side, I'll be pulling my weight providing Pelican Parts with business...
So, it's taken me a bit to get back to this due to having to order the right head for removing the bolts, one of them having been stripped by a prior owner, and having to spend parts of 3 nights working a hex head in, applying heat from a torch, and eventually getting a pneumatic impact driver to get the damn bolt out. Anyway, I did, removed the suspicious axle, and have cleaned out the joints.
Unfortunately, I'm not experienced enough to judge whether or not the joints need replacement, so I've decided to swap the axles left/right since that clearly hasn't been done, and post these pictures of the wear level. If anyone has been through this process and thinks the joints look abnormally worn and should be replaced, please let me know. For now, though, they feel like they fit snugly. I'll put the axles back in tomorrow and see if the noise is present.
Sorry for digging this up from last year but I have the same knocking and symptoms as you did. I'm going to replace the axles too it seems. I first thought it was the DIF but when it started happening again recently I realized it was not coming from the transmission.
For what it's worth, replacing the CV joints alone did it for me. I recall seeing that I could order axles for slightly more and have everything packaged together, but if you have the appropriate tools to tackle the job, it might be worth just ordering joints to save the money. Only one of my joints looked worn, but I replaced them all figuring the others were probably getting close to wearing down.
I'm not sure what your level of experience is, so I'll just mention that the CV joint bolts put up a fight coming off. It's worth getting the right high quality triple square tool for the job. It took an impact gun, a good deal of PB blaster and some torching to get one of mine off. It's also worth getting a few replacement bolts if you haven't. They strip. (Go ahead, ask me how I know.)
I had a warped brake rotor on the side the noise was coming from, which may have compounded my issues, but I've put another 5,000 miles on the car since replacing the joints and haven't had another issue. I'm sure you've done your share of digging through this site, but I believe some others have had similar issues resolved simply by re-packing the joints with grease. My boots had given up long ago, and the grease was mostly clinging to the outside of the boot on one side. (PO must have let the car sit for a while...)
09-23-2015, 02:17 PM
Knocking sound
