Help, noisy rear end suspect diff...

[Fat Audi 80]

The low rumbling started last year, I thought it could be wheel misalignment after my rear subframe refurb or a wheel bearing.
Wheel bearing was not flagged on MOT last year, and the rumbling has got worse.

Had the MOT this morning and asked the guy to pay attention to the rear. No bearing issues at all.

The rumbing is starting at 20mph and gets quite loud by fifty, you can also feel it through the whole car as if the tyre is rubbing on something (it isn't!).

The majority of the sound comes form the NS rear, and if you turn left the noise and vibration subsides a lot, if you turn right it gets a little worse.

I now suspect the rear diff is on its way out.

Any other offers? What is the best way to replace, secondhand, recon etc?

(It actually failed the MOT on both front flexi hoses and some disco effect rear lights which hopefully should be fairly easy to sort...)

Thanks,

Steve

[Acidburn]

If it is the diff then do what s2driveruk did and get a 20v 7a rear diff and swap the flanges over. They have less wear and tear on them than s2 one's.

[mcandmar]

Sounds like wheel bearing on the NS corner to me. Since its been apart first thing to do is retorque the big CV joint bolt, if its loose the bearing will be noisy as you described.

[Fat Audi 80]

Sounds like a good plan. Know anyone with one?

[Acidburn]

with one what?

diff or torque wrench to retorque the bolts?

I have both if you want to try both.

[Fat Audi 80]

Sounds like wheel bearing on the NS corner to me. Since its been apart first thing to do is retorque the big CV joint bolt, if its loose the bearing will be noisy as you described.

Thanks, but the rear bearing has not been apart at all, the subframe was refreshed along with all the bushes and wishbone bushes diff mount etc. The MOT guy cleared the wheel bearing from an MOT stand point. If the bearing was that loud and loose, surely he would have failed it? I could not feel any play in the wheel top to bottom when I had a look....

[Fat Audi 80]

Sorry Pete, cross posted with mcandmar. I may be on the look out for a replacement diff in this case (I have a torque wrench) and the 20v 7a variety sounds like a good idea....

[TimE-J]

Does still sound like a bearing to me. It took a good 6 months of noise until you could hear the noise when turning the wheel by hand. From an MOT point of view, a wheel bearing can only be failed if it is "ruff when rotated" or has excessive play.

[mcandmar]

Its not uncommon for a bearing to be totally silent and without play when jacked up. You need the weight of a car and cornering loads to make them rumble.

[Error404]

Wheel bearing would be my first guess too. As above they need to be pretty ****ed before an MOT man will bat an eyelid

If you want Steve I have a pair of rear hub carriers you could borrow to refurb and fit new beaings in, then it's a straight swap same day etc. Bearings you can get for £25 each

[Fat Audi 80]

Okay chaps, I won't write the diff off yet. It is definitely on one side of the car and changes when you turn from side to side to change the loading on the wheel and the noise rumble builds with speed. My instinct all along has been wheel bearing, but with the MOT pass I had started to doubt myself.

You can feel it through the whole car now, its bloody horrible. It has got worse since I changed the wishbone bushes from stock to Powerflex over the weekend, which would make sense as I have stiffened up the rear end a little more...

Thanks,

Steve.

[andy10v]

You can feel it through the whole car now, its bloody horrible. It has got worse since I changed the wishbone bushes from stock to Powerflex over the weekend, which would make sense as I have stiffened up the rear end a little more...

Thanks,

Steve.

That also sounds like more transmitted noise/rumble from a wheel bearing. I wouldnt have thought wishbones bushes would exaggerate a diff noise?

[Fat Audi 80]

That also sounds like more transmitted noise/rumble from a wheel bearing. I wouldnt have thought wishbones bushes would exaggerate a diff noise?

good point too.

[SE_30]

I'm going with the wheel bearing. During the MOT the car is jacked up to test the play on the wheel bearings so no weight is on them. During the brake test there are a number of other noises that are apparent at the same time, i.e. the rollers, the noise from brake function test itself and general noise from the rest of the garage, you say the noise is only noticeable above speeds of 20mph which will be hard to notice during the MOT.

[TimE-J]

Another way of finding out which bearing has gone is to jack the rear of the car up and spin the wheels by hand, while you spinning the wheel with one hand hold the strut with the other and feel for and ruffness and vibration through the strut. This is normaly a sign long before noise is heard just by spinning the wheel.