Rear Bearing vs. CV-Joint...

[Brad01mc]

Hi!

My '78 SC produces a howling at speed, when turning right, or when the right side of the car is weight loaded, such as when drifting from one side of a lane to the other...think formula 1 cars keeping their tires warm. It only howls when weight is on this side of the car, otherwise, it disappears.

To me, when a bearing goes bad, you can move the wheel in an up/down motion, if you grab the wheel at 12 & 6 O'clock. Mine doesn't do this, however, I did notice that if I hold the rear hub still, and twist the CV-joint, there is significant amount of play and I can feel the bearing slop (the large CV bearings).

So, my question is...

How can you tell a bad CV-joint from a bad bearing? I am begining to think I have a bad CV.

Any comments?

Thanks!

Brad

[kach22i]

Originally posted by Brad01mc
Hi!

My '78 SC produces a howling at speed, when turning right, or when the right side of the car is weight loaded, such as when drifting from one side of a lane to the other...think formula 1 cars keeping their tires warm. It only howls when weight is on this side of the car, otherwise, it disappears.

I have a howling (1977) which goes away in cooler weather, or when I'm rolling slowly up to a stop light and tap the brakes.

From what I've read bad bearings and CV joints make a rumbing sound or clunking sound.

I have no idea what the sound is, may have to post it as a audio file. I don't know what else to do, it's not like I can afford to just start changing parts at random. The car is 30 years old, all the parts could be replaced in my opinion.

I think they call that a "full restoration".

[Joe Bob]

How many miles on the 911? Servicing the CVs might be a good idea. Also eliminates one of the potential areas of concern.

[Brad01mc]

hi!

It just turned 211K!

I agree, might be worth the preventative price.

Brad

[RoninLB]

turning that creates howling is usually bearings. There is considerable slack in still good but worn CVs.

[Grady Clay]

Brad,

Holding the tire at the front and rear and feeling the play is a good test. Seldom can you detect vertical play because of the weight of the wheel-tire-brake-suspension assembly.

It might be productive to remove the wheels and carefully inspect the brake rotors. If a front bearing is mis-adjusted or either front or rear bearing failing, one symptom can be the rotor touching the caliper producing the “screech.” You should look for signs on contact on the rotor or other parts. Inspect the pads for any asymmetrical wear.

Of course the bearings can “screech” but the usual noise for the rear bearing is a “rumble.” If you suspect a rear bearing, check the torque on the axle nut. If it turns to get spec torque, the bearing has probably failed.

With your mileage, it is worthwhile to summarily replace the rear wheel bearings. (This is particularly true with the smaller ’69-’73 rear wheel bearings. The SWB bearings never fail from use – only age.)

Servicing the CV joints is an appropriate maintenance item. You should research the cost comparison between four boot kits and simply replacing the entire half-shafts. The costs of the half-shafts are surprisingly inexpensive. In either case you will want to also replace the CV joint bolts and Schnorr washers. Remember to retorque after 1-200 mi and annually.


Here are some CV joint links:
Pelican rcecale, Randy’s classic thread.
”Reconstructing Constant Velocity (CV) Joints”

“CV Joints”
CV joint disassembly

The following articles are a good reference for Lobro CV joints: Warren Hall
http://volksweb.relitech.com/cvjoints.htm
http://www.type2.com/bartnik/cvjoints.htm
http://forums.pelicanparts.com/show...int+%2Aassembly

I’m all for diagnosing the problem first rather than the “shotgun” approach even when all the items are necessary maintenance.

Best,
Grady

[kach22i]

Grady Clay, nice set of links. - thanks

[Brad01mc]

Hi!

Great! Thanks for all the good info.

I'll have to play around a bit and see what I find out. I definately have enough info to do either job!

Thanks!
Brad