WingleBeast

iTrader: (1)

83 gsl with disc brakes and lsd. Started making a clunk sound when applying load to the drive train about 2 weeks ago, and this week started making a clunking and grinding sound that sounds like from the rear passenger side from the driver's seat. The sound is load and speed depending. Frequency based on the speed, and only off throttle. If I brake or apply throttle the noise will go away completely. It is during straight line driving, no real difference on turns, but hard to tell because I don't really coast on turns.

​​​​My first thought was that I botched swapping the bearings last year, but I jacked up the car and pulled the axels and they are fine. I was fully expecting the drive shaft but it was also fine. With the car on the jack stands I can't replicate the grinding noise. I could replicate the slack in the system and thought that I might have a worn ring gear, but the wheels move less than a cm when I put the car in gear and try to rotate them by hand.

I am at a complete loss and about 24 hours from tearing out the diff to see if I can see any damage in it. I had expected to find a lose u joint or a skip in the wheel rotation like I broke a tooth in the diff. Everything seems fine. Ideas?

mazdaverx713b

iTrader: (91)

Have you removed the driveshaft and checked the u-joints for play or for binding?

LongDuck

Rear spider on the driveshaft. It will gradually get worse over time (and pretty quickly), and eventually get so loud and develop such a bad vibration that you'll know when to replace it. Drop the rear of the shaft after you mark it's flange, and then push, pull, tug on the mount to test the rear joint.

Most likely cause, anyway.

WingleBeast

iTrader: (1)

Those are exactly what I thought, but when rotated by hand had no problems. I'll pull the whole shaft today just to check. Maybe with the car jacked up the geometry on the shaft is hiding the problem.

LongDuck

Plus, your hand won't provide the torque value that may be causing part of the spider bushings to bind.

Lots of people flop the mounts around and call it good, but it beats itself out of alignment as soon as it's hooked to an engine. Report back, if that turns out to fix it...? Helps the next guy who searches on random noises...

WingleBeast

iTrader: (1)

So I pulled the driveshaft and the u-joints seemed tight and smooth, so I dot see an issue there.

I was getting ready to pull the diff and removed the drivers side axle and the bearing was free spinning and rattling. I assume this is as least PART of my problem. I have never had a bearing fail like this, usually they are seized and stuck, which is why I didn't notice.

Would this type of bearing failure not make a sound under load? It is only grinding and rattling during coasting?

GSLSEforme

Can you clarify what you mean by spider and push,pull,tug on the mount. Confused by your terminology. Are you referring to rear u-joint?

GSLSEforme

U-Joint needle bearings? What mount...beating itself out of alignment hooked to an engine? If i'm confused at this terminology,others will be as well.

grotto107

It was also confusing to me

mazdaverx713b

iTrader: (91)

You said tight and smooth for the u-joints. So no binding or rough spots were felt when you moved the joint in a rotational way and a back and forth and side to side motion?

Having a bad rear axleshaft bearing will cause plenty of rotational noise but it will not be load sensitive so much that it will completely disappear. It's nothing like a hub bearing. Load sensitive bearings would be the pinsion bearings. I suspect failure of the front bearing but I would replace the rear pinion bearing as well as other carrier bearings if you pull the differential apart.

LongDuck

When torque is applied to the U-joint, it will put pressure on the bearing that is weak or damaged, resulting in an out-of-alignment condition that can be felt. Sometimes, with your hands, you can't generate as much force as your engine and transmission would, and you won't notice it until it's under engine power.

Clearer?

midnight mechanic

on my car, the rear bearings squeeked as in a squeeky wheel gets the grease when they needed to be replaced

my car sounded like what you describe when the drive shaft u joints were bad. Years later, the **** for brains new jersey transmission guy didn't put the washers back on te trans mount so the drive shaft was too close to the body. Took me a decade to figure out how to fix his f' up.

spider?

WingleBeast

iTrader: (1)

Ok, but we have already established that the drive shaft u-joints are NOT bad.

Other than you own personal stories about your own bearings, is it possible to have a rear wheel bearing cause a load dependent thunk? I am just trying to figure out if I am going to continue tearing this apart for any reason or not. Because the next step is the differential.

GSLSEforme

Let's look at this a different way..starting with fact car is now 37 years old-regardless of mileage. Keeping this car? Sometimes "A" noise is caused by more than one offending part. You said axle bearings recently done and have found driver side bearing loose and rattling,no mention of you pulling right side axle and inspecting it though you say the noise appears to be coming from passenger side of car and also state that applying brakes stops the noise.

Before looking at differential lets focus on axle/bearing/rotor. Before you take anything apart,slip off caliper and mounting bracket on right rear and put a dial indicator on brake pad wear surface and rotate and check for rotor runout in several places on surface,record. Remove rotor and repeat runout tests on axle flange. In 1st test you're looking for a warped rotor,2nd test looking for bent axle/flange. A warped rotor can have effect of knocking brake pads back and forth as warped section rotates thru caliper each revolution. This can cause a knocking noise that quiets on brake apply and may be a sticking/slightly seizing caliper that caused rotor warpage.

Axle/flange may have too much runout from pothole/curb kiss that would exhibit near identical symptoms and again applying brakes quiets noise. 3rd,a sloppy axle bearing,like what you found on left side of car can cause this noise and clamping on the brakes binds everything enough that the noise changes/stops. The fact that axle bearing(s) failed in such a short time could be poor quality parts,bent axle/bent axle housing.
I would do these tests both sides and have some new(quality) axle bearings on hand and if nothing else is found,replace the axle bearings/spacers/seals.Drain rear diff and swim a magnet round in the oil that comes out looking for any shrapnel. Nothing obvious? refill diff(use friction modifier) and roadtest car for noise. Replace what you KNOW to be bad and roadtest.

RE: differential,assuming original...after all these years certain to have lost proper preload on ring and pinion as part of normal bearing wear and pinion crush collar deflection and this along with side/spider gear wear in diff can cause excess backlash which can cause a clunk on decel/accel and attention here should be given only if needed after above tests/repairs are performed without satisfactory conclusion.

RE: driveshaft/u-joints...consider replacing either joints or shaft strictly from age. Even though you feel nothing obviously amiss with manipulating the joints i would believe at least one of the four crosses in each joint would be near dry of grease after all these years and possibly have some rust and needle bearing degradation as a result and this can't be determined without taking the shaft apart. A set of u-joints is not much money,consider this as maintenance,few cars this old haven't had at least one set of u-joints by now.

If this car was in my shop this is exactly how diagnostics/repairs would proceed,not overlooking anything and not repairing more than what's needed.

WingleBeast

iTrader: (1)

Replaced the wheel bearings tonight and diff oil just to be sure. All the brake rotors are in spec, axles are to spec, hubs are good after a good wire brush.

I bolted a plate to one of the wheel hubs and welded a big nut in the middle. I got out my speed handle wrench and got the wheel moving as fast as I could to actually see if I could replicate the sound. Sure enough I could hear a faint clicking. It is cold out in the garage so I called it quits for the night. I know I just hand tightened the driveshaft to remember the flange location so tomorrow I will tighten it and try to replicate again. If it is there I will drop the shaft and try again. If I hear it both times time to pull the diff, if not, the driveshaft.

midnight mechanic

speed handle wrench? Airborne, huh?