CraigandJanet

Well, I'm well into finding that darn chunk, chunk, chunk I hear when running down the road. It should have been narrowed down to the diff, but now I'm not so sure. With the halfshafts removed I started the car and let it fast idle in both drive and reverse. The driveline sounded VERY smooth with absolutely no indication of that chipped tooth or high spot on a gear noise from the rear end. Even with a stethescope I was not able to hear anything but smooth gear noises (I get a bit of whine, normally). I would have thought I'd have picked up something in the driveshaft ujoints or whatever, even if I couldn't put things under load. By the way, the side yokes had very little if any play in and out. There was no vibration evident.

The ujoints on the halfshafts looked well greased and offered no play. They sit quietly on the workbench.

Next I checked the wheel bearings for play. I was never able to notice play when checking with the tires mounted and push/pulling left to right and up and down. My whole rear assembly is very tight. I removed the rotors and checked for bearing smoothness of rotation and play. Both sides show no roughness and rotation is smooth and quiet. The passenger side has absolutely no play. The drivers side shows about .0001-.0002 and even though hardly perceptible, if I pull out on the backing plate and then hit it with my palm, it makes a clack. Putting a lug nut on one of the studs to hold on to and pulling and pushing quickly results in clack-clack-clack over that almost insignificant amount of movement. I can't imagine this being too much play, nor that causing the noise I hear on the road.

My next step is going to be removing the driveshaft and somehow loading the diff side yokes while I turn the pinion, and visa versa. I would think I would feel a high spot, tho probably not anything else.

I am trying, step by step to locate this noise, and as a last resort will pull the diff (big job 'cause some of the exhaust system is welded).

I did seem to notice that my diff fluid was a bit of a grey (metallic? ) color, but still quite clear. I imagine this is somewhat normal with the posi pack and such wearing away in there. The pinion seal does leak a bit. There is no hard clunk when engaging drive or reverse. Obviously I don't want to get into that thing and may be in denial

I'm really open for suggestions on this. The previous owner also heard this noise and replace the rear wheel bearings and all ujoints. Kinda narrows it down, huh? My question - Why cant I hear it in the rear end when the halfshafts are off, when it shows up in coast, float, and light load when on the road - if it was the rear end?

Whew!

MEGALADON

Put in new ujoints and if its still there. put some Gm posi lube
in it. I had the sake CLUNK CLUNK and it went away with posi lube.
It sounded real bad

CraigandJanet

Thanks for the suggestions.

I forgot to mention the noise is there on straight driving, and I get none of the typical posi noises when turning, backing and turning, etc. I will, however add some posi lube, since I think there is some room in there for some (thank you, leak).

I thought ujoints, too, and may yet replace the new, smooth, tight spicers - but not yet.

I can feel this clunking as "almost" a vibration or high speed "knocking" at highway speeds, but mostly at around 35 on deceleration. Almost like a ujoint trunion hitting, say, the front diff mount bolt head (it's not). That's what makes everyone think differential gears. But I ain't getting any noise at all floating it without halfshafts. Odd.

Me thinks maybe it IS that play in the wheel bearing, although the sound doesn't change when essing or turning left or right to load and unload the bearings. BUT, if the angle of the ujoints was such that it caused a slight push/pull on the bearing on each rotation, it might be it. How does one know without popping the spindle and taking absolutely all play out of the bearing with a new shim ground to perfection? I'm going to clean up and double check all the ujoints and also the diff. side yoke play again. It might be a combination.

As we all know, it's a bummer taking these cars apart and putting them back together, so I am trying to limit the excercise as much as possible .

blctalon

What does that one rubber diff-bracket-mount look like? I've heard this can cause noises if it goes bad.

CraigandJanet

Looks pretty supple. I pryed it a bit to see if it was loose and torqued the bolt. Looks fine. Earlier I was thinking that the diff might be tipping a bit forward on decel and the pinion yoke was possibly tapping the bolt head because the clearance is miniscule. That isn't happening.

Everything looks so good under there, that's what's driving me nuts.

Localbulldog

rastadr

does the clunk clunk clunk frequency increase with speed? please check the trailing arm bushings b4 you start tearing more stuff apart

texaswilkins

I just had my 82 towed home for the same noise. That one piece rubber bushing failed on mine allowing the drive shaft to rotate just a little and hit the frame. I know you just checked the bushing but look at the driveshaft this time and see if there are scrape marks on the u-joint ears.

It sounds like all your driveline stuff has been checked. After you took off the half shafts did you look in at the parking brake?

Bill

CraigandJanet

First: Rastadr. Yes, It increases with speed. Trailing arms are solid. I have a hoist in my garage, so it's pretty easy to check things, and I have gone over everything with a fine tooth comb. .

Texaswilkins. That is exactly what it sounds like. I cannot find a mark on the driveshaft, but the clearances are very small. It is louder on coast than drive, and apparent at float (ie., thoughts of differential), quite loud coming down through 40 or 35 mph. I can feel it in the seat of my pants slightly. Running it lifted with all drivetrain and wheels in place you can go thru every component from the tranny tailshaft to the wheel bearings with a stethescope and hear the same noise at the same level - no pinpoint possible. Been to four reputable shops and no one can agree except on expensive teardowns.

I go back to my earlier question of "why would I not hear the noise when running with all the drivetrain in place except the halfshafts" if the problem was truely in the differential?", and now why can't I find anything else out of line or whack, except possibly a rear bearing with .002 slop (well within the .001 - .008 spec). I'm thinking of taking the parking brakes completely out and putting it all back together and trying it. I don't use 'em anyway. Who knows? They look ok, but.......

isosceles

side yoke play? with the halfshafts off, they are no longer loaded. I don't remember what the tolerance is for that. Dan at Van Steel can help with that.

pcfred

big_G

If the diff. hasn't been gone into yet and has high mileage, I would suspect that the carrier or pinion bearings have started to flat-spot. It may not make noise without the load of driving.

mayberg

Has anyone suggested the front diff bushing?

zwede

How about this:

Hook up only one half shaft and run it on the hoist. The posi should be strong enough to turn one wheel without slipping as long as there's no load. Then do the other side. Post back if the noise is there on only one side or both.

I'm thinking it could be something with the brakes (parking or regular). Also try your test with the calipers removed.

CraigandJanet

Mayberg: Front pinion seal leaks so maybe the bushing. I'd think it would make noise when run unloaded, too. Hmmm.

zwede et.al.: I have the rotors off now, so I think I will do a half 'n half, starting with the looser bearing tolerance side. This is getting to be an interesting practice of elimination. I'll keep posting 'cause I know I'm not the only one....

Plus, it's almost 50 degrees here in Michigan (for a couple more days) so nice working without heating the garage.

flood

My chunk chunk was the side yolks rubbing in the diff case. The yolks had worn past their keepers. Your mileage may vary.

CraigandJanet

Well Flood, that may very well be, because I finally got my dial guage mounted properly and measured some things.

The one wheel bearing I was concerned about is at no more than .001. It makes a click if I pull out on the spindle then pop it with the palm of my hand, but I can't even see the play. No play on other side.

The driver side diff yoke pulls out about .002, and makes a metallic click when pushed in quickly. The pass side diff yoke is right at .003, and makes the same click or clack when pushed and pulled to it's limit. Even though these are still JUST within nominal tolerances, I would like to imagine that is my problem since the angle of the halfshafts would cause a bit of push/pull by the ujoint movement. Those two yokes and the wheel bearing (tho I doubt that) would set up the chuncking/clunking clatter I hear. I'd love to slide some hard rubber spacers in between the yoke collar and the diff case and see if that stopped the noise. That would either eliminate that source or define it. (Hmmmm. Wonder how long they'd last)

I have another diff still in the batwing from an 80 (auto) that shows very good tolerances, but I can't use the yokes on my 82. Plus if it is only some yoke noise, I may tolerate it for a while. Even tho my shafts are out, I don't feel like going through all the disassembly required to get the bucket out.

IF that is the source of noise, I MAY be able to lessen the noise (maybe) by a bit of adjustment of the strut rods. I have VBP Adjustable rods, and I think my camber was off a bit. I was able to remove my halfshafts without adjusting the rods out (which you're not supposed to be able to do), so if I adjust them IN just a hair, maybe that will provide some pressure on the yokes and keep them quiet. Maybe. Any comments out there??

zwede

With the car on the ground you will have big forces pushing the spindle and yoke in as that is the upper control arm for the suspension. It should never clack and never move in-out. It is normal to have several 10's of thou play on the yoke (0.010 new and 0.040 used is normal).

There is something else wrong.

CraigandJanet

Aaalllrighteee That's definative, and after much soul searching and head scratching under the hoist, I have to agree. The shafts carry the load and you might hear a "clack" only after being airborn

So here is what we have:

1) In-tolerance two year old wheel bearings with 3K on them.

2) Snug, greased u-joints with 3K on them - driveshaft and halfshafts.

3) No play in the transmission tailshaft and no appreciable leakage (just right to lube things).

4) Leaky pinion seal, but no slop in the bearing.

5) Differential yokes play within tolerance.

6) All diff and wheel bearings turn smoothly and quietly. No roughness.

7) True rotors, new pads, good parking brakes.

8) Absolutely perfectly smooth and quiet running driveshaft and differential with no halfshafts attached.

9) Good bushings on the batwing, transmission mount, front differential mount. New strut rods. New suspension mounting bushings and hardware.

10) No signs of any contact of moving parts.

Sounds like a car I'd like to own so far.....

11) When all together and going down the road: A significant chunk, chunk, chunk or tap, tap, tap, or tug, tug, tug, whatever, that is more evident on coast, there on float and drive to a lesser extent. It is more obvious when decelerating down through the 35 mph range. Sounds like and has the frequency of a high spot on a tooth, a pulled tooth (bent), a chipped tooth. See #8 again.

12) No change in noise when turning, essing, or going straight.

13) Frequency changes with speed of vehicle, not engine.

Looks like I'm going hypoid diving Or put up with it until something breaks and shows itself. Craps.

mayberg

One of the clips on one of my beauty rings is busted, and that ring will click going down the road. Have you considered removing the wheel decorations?

Yes, I'm grasping at straws, but it will be quite interesting when you solve this thing.