Need Help Diagnosing Grinding Noise

NKN84944 · 12-23-2005, 07:12 AM

Well I took the old 944 for a 400 miles trip yesterday from St Paul MN to Chicago and ran a problem. About half way into the trip I started to notice a strange sound, and by the end of the trip it was very pronounced. It is a grinding/resonating sound that appears to be coming from somewhere in the rear. It resonates all the way up through the drive shaft though. The grinding sound is actual speed dependent, and is only present when I give throttle. If I release throttle, engine break, engage the clutch, or put the car in neutral there is no sound. The frequency of the noise increases with speed. If I swerve from left to right the sound remains constant. There are no strange sounds when I engage or disengage the clutch. I put Amsoil synthetic tranny fluid in about 2000 miles ago. Any idea? I was thinking it may be a CV.

This is pretty much the worst time for this to happen as I need to drive it back to St Paul on Monday, and my chances of getting it fixed are slim to none between now and then.

924Sman · 12-23-2005, 08:13 AM

Had a similiar issue. Check the rear wheel bearings, ez to rule them out. Mine was the rear axle nut backed out.

944cabby · 12-23-2005, 08:59 AM

Sounds like cv joints to me.

NKN84944 · 12-23-2005, 09:57 AM

Quote:

Originally posted by 924Sman
Had a similar issue. Check the rear wheel bearings, ez to rule them out. Mine was the rear axle nut backed out.

Yeah I don't think it is the wheel bearing since the noise is only present when I give throttle. I was messing with it some more and it seems to be coming from the right side outer cv joint. I just called around and found a place about 5 miles from me with one in stock so it looks like I will be able to drive it back to St Paul on Monday

I just checked on Clark's garage for a procedure and luckily he has one since all my shop manuals etc are back in MN... Clark is the man!

procon · 12-23-2005, 08:35 PM

Quote:

Originally posted by 924Sman
Had a similiar issue. Check the rear wheel bearings, ez to rule them out. Mine was the rear axle nut backed out.

I've also encountered the same problem, hope it's that simple.

924Sman · 12-24-2005, 01:30 AM

Rear bearing will make noise that is speed dependent. Mine would not make a sound until above 50mph.

NKN84944 · 12-26-2005, 09:54 AM

Well I went out to pick up the CV joint that I needed on Saturday, and when I was pulling out of the parking lot into traffic I gave it a little to much gas and broke my tires loose on the wet pavement. Needless to say the Blizzaks I have on my car gripped like crazy shortly there after and there was a huge bang from the rear

My car then started making a horrible thudding sound so I pulled over and had it towed home. Well I took apart the CVs that night and sure enough two of them were shot... so I replaced them. When I was putting the CVs back on, I noticed that I could spin my rear tires while my car was in gear! I went though all the gears and was able to spin the tires independently of each other in every gear

So it looks like I blew by differential, or maybe something in my tranny. I am sure the noise I was hearing before was my CVs, but it looks like I killed the tranny when the tires gripped after peeling out. All I know is that my synchros weren't very good anymore, and it would be much easier just to drop in a new transaxel.... so I guess its time to start shopping for a new transaxel. Anyone in Chicago land have an early 5sp lying around?

josephsc · 12-26-2005, 10:17 AM

Sounds like a grenaded ring and pinion. When I blew mine, it went with a bang, as well.

While you're under there, you can drain the tranny fluid and if you see bits of metal -- there's your confirmation. If you like seeing carnage, you can go one step further and the differential cover off (passenger side) to see what happened.

BTW, if you're going to swap the tranny and if you drive in the snow, I'd recommend looking for a LSD tranny.

NKN84944 · 12-26-2005, 10:33 PM

Quote:

Originally posted by josephsc

BTW, if you're going to swap the tranny and if you drive in the snow, I'd recommend looking for a LSD tranny.

Yeah I was thinking the same thing. I have never done too much research into the transmissions on our cars, will I have any problems dropping in a later year NA tranny with LSD? I am also planning on doing my clutch while I have the tranny out. I was planning on doing this next summer, but it has turned into one of those infamous "while I am in there" deals