What noises do worn CVs make?

[Lucky]

I started noticing two new noises from the rear this weekend. One is the heater blower (finally got cold enough for heat here in VA), while I'm not sure what is causing the other one.

What kind of noises do worn CVs make? How does the noise change under acceleration vs. engine braking vs. coasting?

Also, do LSDs cause CVs to wear sooner? I have a Porsche unit set at 80% in my 915.

As always... thanks for all the help.

-- John
'86 Carrera

[This message has been edited by Lucky (edited 10-08-2001).]

[Rick Lee]

This may or may not help. I'm not sure if the CV's function too differently in Porsche than in other Euro cars. But I had to replace them in my old SAAB and I correctly diagnosed the problem for a friend's Honda too. The noise that's most common for worn CV joints is a distinct clicking noise when turning the steering wheel. I don't think it will make any noise at all when you're going straight. The best way to hear it is doing a 90 deg. turn under acceleration. With the window down you should hear clicking, almost like a baseball card stuck in your spokes.

[Lucky]

Thanks, Richard.

I'm not getting the clicking sound. This noise is more like a rumble... similar to really noisy tires, but just slightly more mechanical/metallic. At certain speeds it really reverberates within the car. It may just turn out to be worn tires.

Anyone else have thoughts?

-- John
'86 Carrera

[john walker's workshop]

CVs make a repetitive metallic knocking noise, usually when taking off from a stop and turning at the same time. if ignored, they can knock even in a straight line. the noise may come and go. a wheel bearing rumbles and roars as it gets worse. sounds like a bearing by your description.

[Superman]

I agree with John (a pretty safe position since John knows what he is doing). I'll add that the clicking type of CV is the front wheel drive kind that are often asked to operate at very sharp angles. Those kinds have a splined axle shaft that goes through the hub. The 991 kind of CV probably won't click much since it is never asked to operate at very sharp angles.

What I have noticed about the 911-style of CV joint is that they will rumble when worn. Wheel bearings roar, and CV joints rumble. In other words, if you can tell a difference, it's with your butt. Wheel bearings make a lot of noise and sound like a tank. CV joints actually rumble and vibrate the car slightly, but do not make as much noise as a terribly worn wheel bearing.

Also, FWIW, wheel bearings will make a HUGE amount of noise before they completely give up. CV joints will similarly protest (rumble) for a long, long time before they refuse to continue to make the car go. In other words, you could wait and let the problem get worse until it is pretty obvious what the problem is. I know this seems dangerous to many folks, but I have logged a lot of miles in cars with bad bearings and bad CV joints. On a front wheel drive car I would not give this advice.

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'83 SC

[Doug Zielke]

Right you are, Super.
Mrs.Z once had a VW Jetta, and said to me one day: "You should drive my car and listen to this funny noise it's making..."
I said: "Sure, dear...all cars make noises..."
The next thing we knew, the Jetta had thrown a half-shaft!
Lesson learned. Ignore CV's (and wives) at your peril...especially FWD's.

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'81 SC Coupe (aka: "Blue Bomber")
Canada West Region PCA
The Blue Bomber's Website
"If it ain't broke...we'll help you fix it 'til it is!"

[rob justice]

before spending loads of cash - pull back the cv joint covers and pack the cv joints full of graphite grease. the cv joints sometimes 'dry out' which causes the clicking noise as described. (don't overfill cos it makes an awful mess).

[Lucky]

You guys are great! Thanks, John Walker and Superman!

After reading your posts, I drove the car in hopes of better understanding the source of the noise. I'm not certain, but I'm thinking its the bearings as the noise seems to be a function of speed (and does not really change with acceleration/engine breaking/coasting).

I'll check the bearings and CVs tonight.

-- John
'86 Carrera

[CamB]

Yep, if it doesn't vary with transmission it probably isn't CVs.

Try the search function if you think it is CVs and want to service them - lots of excellent advice has been posted (including two very valuable links to VW sites with instructions).

Cam

[Superman]

Here's more of my opinion. If it's a CV problem, then it will rumble less when coasting than when in deceleration or acceleration. Most likely it will rumble on acceleration, but make no symptoms at all on coasting or deceleration. These things should be repacked periodically, and when I repacked mine, I saw that they are worn. Rather than spend the money, I flipped them over. Mark them before removal, and put them back on on the other side of the car. This way, they are wearing on somewhat new surfaces during acceleration. This should get you some more years of service. Find an old Bentley VW manual. The CV section is great. Disassemble, one at a time, and reassemble. Pack with just about as much grease as you can get in there. But I don't think this is your problem. (still, they probably need repacking)

A roaring noise that never goes away and barely changes volume except with the speed of the car is probably a bearing. While you have the CV joints off, spin the wheels and see how those rear bearings sound. Are you sure it's rear? Probably is, but front bearigns are much easier to replace and cheaper too.

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'83 SC