1988 automatic with 60,000 miles
Trying to diagnose a weird sound coming from the car.
I have read as many posts/threads on the forum as I could find but my problem seems a bit unique.
First noticed the sound when travelling down a nice smooth road.
It sounded (and felt) like I was running over joints in the road every 20 feet. Doesn't it do it all the time...seems to come and go.
First suspected the tires; maybe gravel got stuck in the tread.
But then I heard it clunk; maybe more like a thump when pushing the car straight ahead with the engine off and in neutral….doesn’t matter if I move forward or backward, it will make this sound (which I can also feel) sort of randomly.
Not a sound it should be making.
Performed the standard rear wheel bearing check by jacking the car up and grabbing the tires at the 3 o’clock and 9 o’clock positions as well as the 12 o’clock and 6 o’clock positions. The right rear seems to have some play in it compared to the others; fronts are tight; left rear has hardly any movement.
So right now my main suspects are the right wheel bearing and the half-shaft u-joint.
The car makes no clunking when I accelerate or decelerate.
I also considered checking the torque on the axle spindle nut as well as the fluid level in my differential.
Any thoughts would be appreciated.

 

Sounds like a joint is going out along with the right rear as well to me too.

Best thing to do is do them all at once. All the joints and rear bearings. You want Spicer cold forged joints.

 

Joints are easy. Jack it up. Get Under the car where you can SEE the joint to be inspected....

have someone rock the tire back & forth. you can see the joint if its loose. Ifs NOT, then move on to the next.

Its does NOT necessarily have to be a short-shaft.....it can just as easily be the drive shaft. I just went thru that. Heard the clicking, evolved to more of a clunking. Had to get under and watch to see it and PROVE the problem before going to the parts store...
in this case , THAT particular joint and my being old with a body used to collect various forms of arthritis, I chose to let a shop do this one....Short shafts I'll still do. Not that drive line that must be secret 'cause it's hidden under other stuff.

SEE the problem before trying to plan the repair.

I seriously doubt a spindle nut will do anything like this. Almost impossible since it threads the opposite way and torqued to near 200 ft/lbs. You'd feel it doing the bearing grab, anyway.

U-Joint (s)

and Vader is right....do 'em all and forget about it for another 60,000

oh yeah,
regarding he loose bearing....
if you can FEEL it move its time to replace. If you can SEE it move, its time to PARK. Its about to fall off. Don't screw around with these bearings. if you let it go enough it WILL come apart, while driving and it ain;t pretty.

 

I just want to be sure I have to do it now rather than wait...lots of other things begging for my time.
By the way, Vadar86, I did check our your post (with lots of pics) on how to replace the half-shaft u-joints and found it very informative.
Do you have any updated tips?

 

Good advice...I don't think I can see it move, but I definitely can feel it move. I will plan to have somebody assist me to take a closer look at the u-joints as you suggest...I have yet to even visually inspect them.
Also, any thoughts on the differential fluid level?

 

The joints are hard to see slack when you are 3 feet away and trying to move the driveline by yourself. The light is poor and the field of vision is obstructed in every way.
When you can get close with some good light and someone else rocks the wheel you can easily see any looseness in a joint. I searched for the source of the "noise" for 2 weeks as it steadily got worse and worse...I was convinced that I was just gonna have to tear the whole mess apart and start replacing ALL the joints, but I had just done all 4 short shafts 2 yrs before, so I was reluctant to do that. I finally got someone to help and KNOWING the 4 axle joints were new, I started at the front drive shaft joint and sure 'nuff the yoke wiggled quite a bit in the caps...
When apart and on the table the caps did not look all that worn and the needles were all there, but I SAW it wiggling around and a pair of NEW joints in the drive shaft solved the problem...so, they were just worn to the point of being too loose to be any good. I use the non-serviceable just because its a huge hassle to use a needle to grease the joints after they are installed. The zerk-less joints are supposed to be stronger too, because they are solid.



The diff fluid level is a judgment call....

many folks say IF fluid drains out when you pull the plug its good. Some others say if you can touch fluid with a finger its ok.

Ok...? 2 pretty different levels considering this thing does not hold too much fluid ! 1 oz is a bunch to a Dana differential !

I guess it has to be over-filled for fluid to run out? I dunno how else its gonna be able to spill when the plug is removed..

I've sucked mine a few times and re-filled with fresh lube mixed with posi-additive. That's ANOTHER judgment call. How much additive vs the actual lube? Unless the diff is 100% empty, there is no way of knowing what is the correct amount. Use your best judgment there as well.

What I do, and it is a PITA but its effective, I lean the car with the floor jack and suck as much as possible. I use the syringe type of sucker with hose that's reduced down to 1/4" hard plastic so it gets down inside the diff as far as possible.
The fluid MUST be warmed-up from driving or the only thing that's gonna suck is the results.

anyway, assuming you get most of the old stuff out, and leaning the car to that side helps, I then do the opposite and lean the car the other way so the filler is high.
I'll make my guess at the posi stuff, add that to a qt of lube and I use a hose to enter the diff that's connected to a funnel that I have hanging from a work-mate stand next to the car so I can fill the funnel and let it drain into the diff without laying under the car.

I fill till it runs out the filler then I'll add a bit more...so its trying to really pour out the filler hole. yank the hose out, stick the plug IN.
I KNOW its full now...

and yes, next time I check it, fluid WILL run out of the filler hole as advised !

This diff has lots of miles on it and the fluid is staying green and clean for 50,000 or more. The diff has 300,000+ miles on it...stock and has no leaks, no problems. Quite possibly due to the fact that I DO change the fluid and keep up with the additive for the clutches...the only real wear parts in the differential.

Next time I have the batwing out, or the diff finally fails, I will add the drain plug to the thing. There is a simple template circulating around here somewhere that shows where to drill out a hole and tap it for a drain so its at the bottom, in the low spot and away from everything. This is for when the diff is apart so no metal gets chewed up by the gears.

Hope this helps.

 

Yes it does.
I noticed that the Haynes manual does not give the size of the allen wrench for the filler plug, nor does the factory service manual. Another book I have says you need a special tool.
So what should I be using?

 

one thing I have seen tons of joints bad and froze up to where there is no play in fact it is pretty common for joints that do not have a lot of movement while they are turning like the rears on the vette. so dont hold it does not have play as a rule it must be good because it could be frozen solid and you will not get movement. Also with the engine cut off and coasting it would not surprise me that you are getting a clunking noise. There is a good chance that you have play between the ring and pinion ( not uncommon with cars with some millage) and free coasting like that puts a no load on the rear and any play is going to be heard. Wheel bearings should be no play. If you have play I would replace them and do the joints at the same time.

 

I looked for a long time on my '94 when I had some vibration and occasional noise. The u-joints looked and felt tight. I finally got some worse sounds at low speed that were almost a grinding noise. I pulled the half shafts and the u-joints were trash. They were corroded and some of the needles missing and others mangled. It was a mess, but the joint looked and felt solid when on the car.

 

if you deside to go the ujoint route I posted not to long ago a way of doing it where you dont have to remove the crap the is suggested. In reality you only need to remove the 4 straps. Look for my post if you go the ujoint route loook up my post of messgae me if you wish to try my way

 

I finally got around to removing the filler plug (which I discovered is a 3/8" allen, not 10mm). Needed to attached a 12" pipe to get enough torque to break it loose.
I stuck my pinky finger in and came up with nothin...
So I pumped in some Castrol Limited-Slip 80W-90.
It ended up taking a bit more than a quart so I figure it was more than half empty...not good.
I hope that didn't cause any damage.