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rockhound72 · Posted: Tue Dec 18, 2012 9:22 am Post subject: Road noise mystery

I noticed about a week ago, a roaring noise when I'm driving my '79 924. It is mostly a dull roar, and it cuts out when I make left turns. The noise is noticeable when driving over 45 MPH. My first thought was wheel bearings, passenger side. After removing the tire, the bearings looked in good shape. I put the wheel back on and check for tire play. No matter how I shook the tire, it was stiff. OK, I thought, it has to be the rear. Nope, I checked the play on all four and nothing. The roar also comes and goes when driving straight and if you hit a dip in the road, it stops. The tires are inflated to proper size also. Basically, I am at a stopping point and thought I would ask the experts. I await your wisdom.

Smoothie · Posted: Tue Dec 18, 2012 9:48 am Post subject:

Possibly the CV joints? Though when they went on mine, the sound was more of a rythmic clunk, bang or knock. -And it would come and go with changes in accelleration, and obviously increase in frequency with higher speeds.

Another possibility that would fit with your description of a "roaring" sound would be tire/s rubbing the upper inner side of the fender. A common 924 manufacture anomoly leaves the rear left tire closer to it's fender and more likely to rub.
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"..it's made in Germany. You know the Germans always make good stuff."

'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox

rockhound72 · Posted: Tue Dec 18, 2012 1:57 pm Post subject: not a cv joint

I had a cv joint go out a few weeks ago. Completely different noise, so I can rule that out. Never heard about the tire issue. I will check the wheel wells. Seems like I would have heard it earlier than this. Of course I blew out my muffler and exhaust gasket, so I really couldn't hear anything for a week.

fiat22turbo · Joined: 18 Jan 2006 Posts: 4040 Location: Portland, OR

On my 924, the rear is shifted to the right about 1/4". Luckily, there's adjustment built into the rear suspension to dial this out (also, I had it all apart awhile ago and just now checked it since I've not done a full alignment on it yet)

So yeah, it could be a tire rubbing or something that's shifting enough at that speed to cause it to rub.
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Stefan
1979 924 Carrera GTS (clone-ish)
1988 944 Turbo S (Silver Rose)

!tom · Posted: Tue Dec 18, 2012 4:09 pm Post subject:

How can you be confident the bearings are fine after removing the tire? Your description certainly does sound like wheel bearings, and it may warrant closer inspection.
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78 924 NA
5-lug

fiat22turbo · Joined: 18 Jan 2006 Posts: 4040 Location: Portland, OR

As to your rnoise problem? Definitely sounds like a wheel bearing starting to go out, not likely bad enough to be loose, but starting to break down. It happens, time to buy the bearings (I would replace both sides at the same time) and tools, then plan a free weekend to change them out.
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Stefan
1979 924 Carrera GTS (clone-ish)
1988 944 Turbo S (Silver Rose)

emoore924 · Joined: 13 Apr 2004 Posts: 2815

I'd go with WB too. Or tires (specifically, tire wear, the "over a bump" comment kinda leads me there). But also consider torque tube.

Easiest thing would be to rotate your tires and see if the noise changes, moves or goes away.

DOCO · Posted: Wed Dec 19, 2012 5:38 am Post subject:

Sounds more like a differential brg .in the trans.as you say the noise comes and goes on acel and decel.Wheel brg would not do that it would be constant,but change under turning load. a diff. will change under turn load and accel and decel.
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Doco "where am i going and why am i in this handbasket"author unknown
79 924 N/A "Webster"
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"WEBB STR"

rockhound72 · Posted: Wed Dec 19, 2012 2:11 pm Post subject:

Took the passenger front wheel bearing off and cleaned it up. The grease was almost like glue, so I think I will work my way around and inspect and repack or replace. The bearings were in great shape. Tomorrow I will tackle the rear bearings. From what I have found from hours of post searching, I definitely need a good torque wrench (which I do not have).

I will pester my neighbor again. Now I know what I need for Christmas! Besides a paint job. I will post the culprit when I find it for future people's reference.

!tom · Posted: Wed Dec 19, 2012 4:58 pm Post subject:

The rear bearings don't need a torque wrench all that badly, as a torque wrench is a calibrated tool used to tighten accurately. Rather, you'll need a breaker bar or a really big impact wrench to deal with the castle nuts, as they're supposed to be in the 300+ ft-lb range.

Note, you'll also have to pull the CV axles if you're going to remove the rear drive axles (which you need to do if you're going to access the rear bearings).
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78 924 NA
5-lug

emoore924 · Joined: 13 Apr 2004 Posts: 2815

+1 on the really big breaker bar for the rear WBs. You also need the RIGHT socket to get that castellated nut off. I have one, I think its 36mm maybe, that's air hammer hardened and gets the absolute **** beat out of it with a 500lbft snap-on air hammer whenever we have to do the rear wheel bearings.

Not a job for the faint of heart.

rockhound72 · Posted: Fri Dec 21, 2012 5:23 am Post subject: finally

Well, the culprit is definitely the rear passenger wheel bearing. It wasn't showing enough wear til today. Have to take it to my buddy's place to get that knuckle busting pain in the @$$ castellated nut off. I know what I get to do for Christmas now! To the rest if ya... Have a Wonderful Christmas and a Smashed New Year!

fiat22turbo · Joined: 18 Jan 2006 Posts: 4040 Location: Portland, OR

Yeah, I used a 3/4" drive socket set and breaker bar with a 6-foot piece of fence pipe to break mine loose. It wasn't fun.

Neither was pulling the old bearing out or putting the new one in. Since I have aluminum arms, I had to heat the arms up, which takes forever to do and I set my arm on fire in the process.

Next time? The f-ing arms are coming off and its going to a machine shop!
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Stefan
1979 924 Carrera GTS (clone-ish)
1988 944 Turbo S (Silver Rose)