andy@utzoo.UUCP (Andy Rubaszek) (06/29/83)
I am at my wits end trying to find where a weird, unpredictable noise is coming from. The noise is a sort of muffled whirring that appears to be coming from the differential (or at least from the rear end). The car is a 1979 Olds Cutlass wagon with 70K miles on it. These are the things I have checked so far with no luck: a. prop shaft and u-joints (balanced and look ok) b. transmission and speedometer drive gear c. rear tires and brakes d. differential fluid level (it was low, but topping up made no difference) e. rear wheel bearings sound ok (I haven't taken them out tho) f. new pads on front discs; calipers and rotors ok g. front wheel bearings are not great, but more or less ok. The noise develops at about 30 mph and remains steady until around 35 mph when it goes away only to reappear at about 55 mph (well, sometimes 60 mph, but I don't want to get yelled at). It SOMETIMES goes away when I apply the brakes or there is a curve in the road (left or right). It is most pronounced when I am just maintaining speed (more or less coasting). I finally gave up and went to a reputatble mechanic who said it sounds like "something" in the differential. He suggested I put in some Moly-slip additive. I did, and it didn't do a thing. So, the mechanic is stumped and I am getting fed-up. I don't know where else to look, and the thought of spending a few hundred bucks to strip the rear end only to perhaps find nothing is wrong is my last resort. Has anyone had a similar problem or can offer some advice? The latest advice I got was to wait until the noise gets very bad or the "something" breaks. Any comments?
ms@houti.UUCP (07/01/83)
Eat less beans and sauerkraut ! To add odour to the noise - drimk Marston's Pedigree ( English Beer ). Martin. (Flying Circus Fan)
chichak@auvax.UUCP (07/06/83)
This sounds like the typical(sp?) BMW (or any) differential problem. The pinion shaft bearing is wearing out. If it is taken care of early enough you can spare yourself the cost of a new pinion shaft/gear and maybe even crown gear. Thats my, educated, guess. more later Andrei Chichak auvax!chichak
wookie@alice.UUCP (07/11/83)
I have had similar problems in three high mileage rear axles nad from your description I would say the input pinion gear bearing may be failing. In all my cases it wound up being cheaper to get another axle from a junk yard and just replace the whole thing rather than try to replace the bearing since this requires careful setting of clearances between the ring and pinion gears. The fact that the fluid level was low may give some clue. One of my failures was due to a leaking axle seal which I ignored until I could get to it. In the process the fluid level dropped and I presume lack of lubrication caused the failure of the pinion bearing. So look for a leak either at each rear axle (remove the brake drum and you should not see any oil on the backplate) or at the input shaft (look for oil sprayed around the area where the universal joint is at the input to the differential). While you're looking at the input shaft see if it has any side to side play in it. If it has noticeable play then it is indeed the pinion shaft bearing that is failing. In all my cases the failure time was about two weeks of driving to and from work from the time I first heard the noise until the car was no longer driveable. The noise I heard occurred mainly during deceleration and so near the end when the noise got really bad (due to grinding of the gears inside) I had to drive with the rear axle constantly under forward load. This meant no backing up at all, not decelerating to reduce speed but using the brakes with the engine applied and definitely no coasting! Well I hope this gives some insight and who knows maybe it's just a noisy positraction unit like in my Trans-Am but then you didn't say it goes clunk, clunk, clunk when making a turn but is fine otherwise. Good luck and let us know the results! Keith Bauer White Tiger Racing