Mysterious clunk

[adallak]

First, Fleetwood is an RWD Cadillac.

When I pass at low speed by a building or even curb I can clearly hear clunks in rapid succession definitely correlated with rotation of wheels. I cannot determine whether it is front wheel (wheels) or rear ones. If apply brakes slightly clunk goes away.

I assume it is on the passenger side, but who knows... Unfortunately, I rarely have passengers to ask them to pull down the window and identify the location of the clunk or clunks.

Today I jacked up the front right wheel and checked it for play. There was no play in 9 - 3 direction and less than 1/8" when I grabbed the wheel at 6-12 position. I also checked the lower ball stud and it was fine (the grease fitting was even with the surface of the stud).

I checked the caliper and it was not loose. The only thing I did not like was the outer pad - I could easily move it some 1/16" in vertical or horizontal directions. I do not think there were ever any antirattle shims installed. I can assume that loose pads can rattle if you hit a pothole, but I cannot see how it can make that annoying clunk-clunk-clunk noise on smooth pavement.

As far as I noticed the clunk is more pronounced when front wheels are not straight (on curves).I have also jacked up the rear passenger wheel. It only had some 1/16" axial play - I could pull it out and push it in some 1/16" and it would clunk. Is it normal play? There was no play in vertical or horizontal directions whatsoever. I am at a loss. The noise is very annoying.

Sorry for a long post. Any thoughts, gents?

[Cadillac Jim]

Sounds like a CV joint to me. I don't know what the rear wheel axial motion spec would be, but I would suspect that it is zero. Whether a 1/16" slack would mean that a repair is indicated, I could possibly look up in the FSM if they have that spec with service limits.

[CoupeDTS]

I had a similar clunking pop up a couple months ago on my fleet, sounded like something dragging under the car or hitting floorboard. It was the front passenger wheel bearing that was a year old. Cant believe it, sounded just like something dragging and clunking. Shouldnt have used the cheapies, I put in the good ones this time. Right side stuff always goes out first because of the edge of the road being rougher, more pot holes and all the crap on roads goes to the sides so that side of the car gets beat up more. Even without play in the wheel I would suspect the wheel bearing is starting to go out. Its a cheap easy fix so if it were me I would probably change it anyway. I would try to confirm which wheel it is though. If its the back, those wheel bearings arent as fun to change lol.

Only other clunk i had was also this year and I could tell it was my back wheel. A spring in the drums and the retainer that holds the shoes to the axle had broke and caused some squeeling clunking in there.

I would definately lean towards wheel bearings though.

[Cadillac Jim]

In a 1995 Fleetwood, you may have trouble finding a part number for the wheel bearing. I believe that Cadillac sells it as an assembly with the hub. If you can find a replacement, a good machine shop can pull the old one and press in the new one.

[johnnyjaws]

i had a scraping noise on my 98 deville it was the front rotor dust plate it was bent on the bottom of the rotor scraping aganist it

[adallak]

Thank you gentlemen for the comments. I absolutely hate to play with wheels on this car, but what can I do... Wheel bearing sounds possible because the periodic clunking noise is direction-dependent. The dust plates are fine. Steering concerns me too, but that is a different story. I will always find something to be concerned with! LOL

[Cadillac Jim]

If only wheel bearings, CV joints, and such could throw a code.

[adallak]

If only wheel bearings, CV joints, and such could throw a code.

Jim, as far as I understand CV joints are on front wheel vehicles. No?

[BodybyFisher]

If you didnt say CLUCK, I would have thought brake pad chatter also.

Have you pulled the front wheels?, are these similar to the hub bearings used in the rear of front wheel cars (sealed contained units), where is the 1/8th play coming from?, the bearing?

[Cadillac Jim]

CV joints are used on all front-wheel vehicles because of short half-shafts that require significant angles across the joint which would cause a driveline shudder if ordinary universal joints (U-jounts) were used. Ordinary U-joints are used in most RWD vehicles because the angle across them is usually small enough so that pulsations in drive torque and RPM are very small. But, when independent rear suspension is used as is done in just about all cars nowadays (with curious, notable exception of the Mustang), the rear axles require CV joints too. And, some RWD or 4WD cars with short drive shafts or long rear suspension travel also require CV joints at one or both ends of the drive shaft(s).

In summary, CV joints are the rule rather than the exception nowadays. The highest stress point in the chassis for CV joints is the front axles, particularly in FWD cars (as opposed to 4WD cars) because high torque at high angles between the shafts is an everyday reality there.

For Cadillac and GM in general, CV joints rarely give trouble if their boots are seals are in good shape. If the boot is cracked, loose, or broken, it should be replaced and the CV joint cleaned, inspected, and lubricated as appropriate ASAP to head off CV joint damage. If you see a trace of grease at a seal in a CV joint that isn't in a boot, you should probably plan for the repair in the near future.

[adallak]

If you didnt say CLUCK, I would have thought brake pad chatter also.

Have you pulled the front wheels?, are these similar to the hub bearings used in the rear of front wheel cars (sealed contained units), where is the 1/8th play coming from?, the bearing?

Mike, the bearings are different. They are tapered not ball bearings. The less than 1/8 play is in the front wheel 6-12 position, which is within specs.

The other 1/16" AXIAL play is the play of rear axle. The FSM points that kind of periodic clunk approximately every two revolution of the axle to worn rear axle shaft bearing. What a headache... I am afraid if I keep driving like that , the differential will fail as well.

[airmike]

If only wheel bearings, CV joints, and such could throw a code.

Jim, as far as I understand CV joints are on front wheel vehicles. No?

adallak have you checked the u-joints? Your car surely has both if the rear is independent. The drive shaft would still have u-joints.

[Cadillac Jim]

Pardon my wordy post on #10 on this thread:

http://caddyinfo.ipbhost.com/index.php?showtopic=38708&view=findpost&p=190629

CV joints are used on both front and rear axles where there is independent suspension. They are sometimes used in the drive shafts of 4WD vehicles when there is significant bend angle across the joint, or there is a lot of thrust force as in axle shafts.

U-joints are most often simple X castings with a U on both sides, coupled by pin bearing joints. CV joints are dual joints with an outside housing that couples two U-joints at right angles to each other or other more complex designs. When there is a lot of thrust force, the bearings are more than simple pin bearings and are usually sealed roller or tapered roller bearings, and there will be an alignment mechanism for the outer housing, which supports the joints on both ends. This is an oversimplified description; see the Wikipedia article for more and better information:

http://en.wikipedia.org/wiki/CV_joint

GM probably uses the Thompson Coupling, or TCVJ, on the axles. The simpler Double Cardan is used in the steering column, with tilt-wheel cars and such. The more elaborate designs, like the Rzeppa CV joint, were used in early small British FWD cars in the 1930's but I doubt their durability is sufficient for big, powerful cars.

[adallak]

Pardon my wordy post on #10 on this thread:

http://caddyinfo.ipb...ndpost&p=190629

CV joints are used on both front and rear axles where there is independent suspension. They are sometimes used in the drive shafts of 4WD vehicles when there is significant bend angle across the joint, or there is a lot of thrust force as in axle shafts.

U-joints are most often simple X castings with a U on both sides, coupled by pin bearing joints. CV joints are dual joints with an outside housing that couples two U-joints at right angles to each other or other more complex designs. When there is a lot of thrust force, the bearings are more than simple pin bearings and are usually sealed roller or tapered roller bearings, and there will be an alignment mechanism for the outer housing, which supports the joints on both ends. This is an oversimplified description; see the Wikipedia article for more and better information:

http://en.wikipedia.org/wiki/CV_joint

GM probably uses the Thompson Coupling, or TCVJ, on the axles. The simpler Double Cardan is used in the steering column, with tilt-wheel cars and such. The more elaborate designs, like the Rzeppa CV joint, were used in early small British FWD cars in the 1930's but I doubt their durability is sufficient for big, powerful cars.

Thanks Jim. I'll check those links out. There are no CV boots on my car, so I assume they use simplified constant velocity couplings.

[adallak]

If only wheel bearings, CV joints, and such could throw a code.

Jim, as far as I understand CV joints are on front wheel vehicles. No?

adallak have you checked the u-joints? Your car surely has both if the rear is independent. The drive shaft would still have u-joints.

Airmike,

No I did not check the u-joints. Do not even know how to do that. Need to read up the FSM. But if you can give me some quick hints, that would be just great!

[PAUL T]

If only wheel bearings, CV joints, and such could throw a code.

Jim, as far as I understand CV joints are on front wheel vehicles. No?

adallak have you checked the u-joints? Your car surely has both if the rear is independent. The drive shaft would still have u-joints.

Airmike,

No I did not check the u-joints. Do not even know how to do that. Need to read up the FSM. But if you can give me some quick hints, that would be just great!

I always checked my u-joints by shaking to see if there is play or turning them to feel if the rotation is rough. In my experience when u-joints go bad you will have a vibration or grinding noise not a clunk.

[adallak]

If only wheel bearings, CV joints, and such could throw a code.

Jim, as far as I understand CV joints are on front wheel vehicles. No?

adallak have you checked the u-joints? Your car surely has both if the rear is independent. The drive shaft would still have u-joints.

Airmike,

No I did not check the u-joints. Do not even know how to do that. Need to read up the FSM. But if you can give me some quick hints, that would be just great!

I always checked my u-joints by shaking to see if there is play or turning them to feel if the rotation is rough. In my experience when u-joints go bad you will have a vibration or grinding noise not a clunk.

Thank you. No vibration or groaning whatsoever. Probably not bearings. I will first fix that loose outer front disc brake pad and see if it eliminates the clunk. The theory is that the rotor picks the loose pad up and then it drops back making a clunk. Later the rotor picks it up again and so forth... If that is the case I will be so glad. If the theory is correct, there should be no clunk in reverse movement. I never checked that.

[Cadillac Jim]

Now that I think about it, my 1966 Corvette had two humongous U-joints on each axle, oriented 90 degrees from each other. Thus the two U-joints and the half-shaft constituted one big CV joint. That may still be done in some cars when half-axles are short and have a flex joint at *both* ends (full independent, not swing axle).

[airmike]

After rereading your initial entry I would doubt u-joints also, depending on your definition of a clunk. What I would describe having heard many times next to a curb or building at low speed would be a creaking/groaning noise that comes and goes with maybe every half wheel rotation. Also similar to a bunch of crickets. I have heard a loose wheel make this same noise. It would definitely be heard as a clunk when you change directions with the transmission. If that is the case I would take the drive shaft out and check for binding joints. If the noise is a clunk in continuous forward motion then I doubt u-joints.

[adallak]

After rereading your initial entry I would doubt u-joints also, depending on your definition of a clunk. What I would describe having heard many times next to a curb or building at low speed would be a creaking/groaning noise that comes and goes with maybe every half wheel rotation. Also similar to a bunch of crickets. I have heard a loose wheel make this same noise. It would definitely be heard as a clunk when you change directions with the transmission. If that is the case I would take the drive shaft out and check for binding joints. If the noise is a clunk in continuous forward motion then I doubt u-joints.

Thank you. I'll first fix that loose outer brake pad and see. For some reason, I think it is the problem. I'll report back in a couple of days. It is raining here.

[WarrenJ]

I cannot determine whether it is front wheel (wheels) or rear ones. If apply brakes slightly clunk goes away.

[...]

Any thoughts, gents?

I'm guessing you could isolate it to the front or rear wheels by simply applying the parking brake to activate only the rear brakes. No?

Also, no insult intended here . . . but are all your lug nuts secure?

Regards,

Warren

[adallak]

I cannot determine whether it is front wheel (wheels) or rear ones. If apply brakes slightly clunk goes away.

[...]

Any thoughts, gents?

I'm guessing you could isolate it to the front or rear wheels by simply applying the parking brake to activate only the rear brakes. No?

Also, no insult intended here . . . but are all your lug nuts secure?

Regards,

Warren

Warren, that was a great idea, the parking brake. Yes, all lug nuts are tighten to the specs.

[KHE]

The RWD cars use U-joints so there are no CV joints or CV shafts. The hub bearings are tapered roller bearings and a separate reluctor ring on the brake rotor for the ABS system - completely different from a FWD application. From the description of the noise, I wouldn't think those components are causing the issue.

When u-joints are bad, they seem to make a loud clunk when shifting from reverse to drive.

The outboard brake pads on the RWD cars need to be "clinched" so they do not rattle. A chisel is placed between the rotor and the pad and the tabs are driven toward the caliper with a punch and hammer. That is the procedure in the shop manual but I have found that it is difficult to get them tight enough. I bend the tabs before installing the pads in order to obtain a tight fit. It is possible the issue is the outboard pads but I'd think the brakes would squeal vs. clunk with loose pads.

[adallak]

The RWD cars use U-joints so there are no CV joints or CV shafts. The hub bearings are tapered roller bearings and a separate reluctor ring on the brake rotor for the ABS system - completely different from a FWD application. From the description of the noise, I wouldn't think those components are causing the issue.

When u-joints are bad, they seem to make a loud clunk when shifting from reverse to drive.

The outboard brake pads on the RWD cars need to be "clinched" so they do not rattle. A chisel is placed between the rotor and the pad and the tabs are driven toward the caliper with a punch and hammer. That is the procedure in the shop manual but I have found that it is difficult to get them tight enough. I bend the tabs before installing the pads in order to obtain a tight fit. It is possible the issue is the outboard pads but I'd think the brakes would squeal vs. clunk with loose pads.

Thanks Kevin. There is no loud clunk when switching from reverse to drive.

The caliper bolt required a 3/8" hex wrench which I did not have. Bending the tabs with the pad on the caliper did not look like a good idea to me, so I will wait till I get a wrench to adjust the tabs off the caliper. Here is a video of the loose outer front brake pad. >http://www.youtube.c...h?v=e8p4KbOHOAo

[KHE]

The RWD cars use U-joints so there are no CV joints or CV shafts. The hub bearings are tapered roller bearings and a separate reluctor ring on the brake rotor for the ABS system - completely different from a FWD application. From the description of the noise, I wouldn't think those components are causing the issue.

When u-joints are bad, they seem to make a loud clunk when shifting from reverse to drive.

The outboard brake pads on the RWD cars need to be "clinched" so they do not rattle. A chisel is placed between the rotor and the pad and the tabs are driven toward the caliper with a punch and hammer. That is the procedure in the shop manual but I have found that it is difficult to get them tight enough. I bend the tabs before installing the pads in order to obtain a tight fit. It is possible the issue is the outboard pads but I'd think the brakes would squeal vs. clunk with loose pads.

Thanks Kevin. There is no loud clunk when switching from reverse to drive.

The caliper bolt required a 3/8" hex wrench which I did not have. Bending the tabs on the caliper did not look like a good idea to me, so I will wait till I get a wrench to adjust the tabs off the caliper. Here is a video of the loose outer front brake pad. >http://www.youtube.c...h?v=e8p4KbOHOAo

You bend the tabs on the outer brake pad, not the caliper. One of the tabs is visible by your thumb in the video. I use some large channel locks and adjust the tabs on the brake pad so the pad is tight when snapped into the caliper.