Rear Diff Knocks on corners

[Highway-Star]

As the title suggests, I have a knocking noise coming from my rear diff, but only when i'm cornering, and it happens at any speed.

MY car is a 91 Sierra Widetrack, mainly stock (drivetrain anyway). My father reckons when sitting in the rrear seat he can just feel the knocking through the floorpan (moor-so to the righthand side).

I've jacked it up and rotated the rear axle (one wheel one way, other the other) and the noise echoes along the length of the whole axle housing.

The rear right hand side outer bearing was replaced two years ago, but we doubt its bearings because it only occurs on corners. For now my father and I are thinking that it is the diff centre itself, probably spider gears, only having problems when the diff differentiates.

Has anybody got any other opinions or have had the same issue, I'm going camping next week towing a trailer up the beach. All other posts on the forum don't fit my particular issue. (Sorry about the length of the post).

Thanks, Aaron.

[mistaboz]

Id be checking bearings first.
If not that then pull the diff out and have a look.
Just because it doesnt make a knocking sound in a strait line doesn't mean its not a bearing.
Good luck.

Cheers Paul..

[Hottuna]

For the price of the oil, drop both the plugs out of the rear diff and check for metal filings stuck to the bottom plug or in the oil.

I think you can just see the crown gear by looking through the rear filler hole with a torch so it might be worth checking to see if you've dropped a tooth or two off the crown.

If it was a bearing that was making the noise you describe you should be able to feel at the end of the axle when you rotate each side by hand.

Cheers

[bazooked]

wheel bearing.

[Highway-Star]

Thanks Mistaboz and Hottuna for the replies.

Also with against the bearings is the when jacked up there is minimal play in the wheel. Could it be the inner bearings (in centre), or the pinion bearing? If it is bearings it must only effect the axial properties of the bearing (cornering would axially load the bearings). Ball bearings are used in the rear outer correct?, with tapred rollers in the inners? To me this means the inners are designed to take the axial loading (ball types have poor axial loading properties, whilst tapred rollers are designed for this). My point is I would think that the inners would be more of a chance, and to check these the whole centre must be removed, so I could guess I could check the diff anyway.

Hottuna's suggestion, I think i will drain the oil out in the morning and rotate the diff around (If i can see the crown wheel). I've got plenty of spare gear oil in the shed.

If something is really buggered, I'm thinking getting ahold of an entire rear diff housing and rebuilding it completely, then swapping it in. I've just got to confirm if my diff centres are 3.9s, as it took 27" tyres to get my speedo almost correct (standards give me slower than GPS reading).

Another question, taking it easy, would people think it safe to have my camping trip next week, and pull her apart after, or does this sound like asking for trouble?

[lay80n]

It takes no time at all to rip a centre out of a WT, so if your wheel bearings are okay, then rip the sucker out. Remember that the factory speedo on all cars is optimistic, so if there only was a small difference from the speedo to the GPS it was probably normal. Usually if the crown wheel had missing teeth you get a clunk all the time, not just on corners. Check your wheel bearings first (outers can cause this noise) then check your centre.

Layto....

[Highway-Star]

Problem appears to be solved

I drained the oil this morning (clean and acceptable levels of metal on plug magnet [film not chunks]). Anyway proceeded to begin removal of LHS axle to check outer bearing and noticed that the 4 bolts that hold the brake drum on were not very tight.

Tightened up these bolts, but everything back together, and went around the block; no noise. I guess I over reacted yesterday, but that still concerns me that suddenly my brake drum became loose (owned the car for around 2 years and never touched the LHS axle). I will be going and buying some new spring washes for the 4 bolts, and I'll still keep an ear out for any noises in the future.

Thanks guys, If wheel bearings were not repeatedly suggested I may not have done this today and found the prob.

[Highway-Star]

sorry, Nuts not bolts.

[lay80n]

Problem appears to be solved

I drained the oil this morning (clean and acceptable levels of metal on plug magnet [film not chunks]). Anyway proceeded to begin removal of LHS axle to check outer bearing and noticed that the 4 bolts that hold the brake drum on were not very tight.

Tightened up these bolts, but everything back together, and went around the block; no noise. I guess I over reacted yesterday, but that still concerns me that suddenly my brake drum became loose (owned the car for around 2 years and never touched the LHS axle). I will be going and buying some new spring washes for the 4 bolts, and I'll still keep an ear out for any noises in the future.

Thanks guys, If wheel bearings were not repeatedly suggested I may not have done this today and found the prob.

Mine used to do this randomly too. I put new spring washers on them and loctite. No problems since.

Layto....

[Highway-Star]

Hey thanks Layto, feels good to not be the only person with a peculiar problem. Got the spring washes (10c each), should have some loctite in the shed.

[Impulsive]

Damnit. I only just spotted this post, and I was going to suggest that you stop going around corners.

Oh well...

Good find there, dude. Better safe than sorry.