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MG MGB Technical - Growling Differential

Hi,
I have recently put the top up on the '71B and as usual I now get to hear all the wonderful transmission noises, including the usual growl from the differential on over-run. I don't know if it's my imagination, but this year it sounds louder than in previose years. I know next to nothing about diffs, so can anybody suggest where the problem may be.

Cheers
Ken Martin

That growling is usually a sign of a worn ring and pinion gear due to a lack of lubricant in the rear axle. Due to the cost of replacing the parts it is usually cheaper and easier to find a good used unit. They are plentiful and fairly priced. I hope that I'm wrong. RAY
rjm RAY

I checked the oil level back end of last year when I put it to bed and the level was ok. I think the growl has been there since I bought the car to some degree, it's just getting worse. I'm afraid it's going to have a long wait for a new axle.
Cheers
Ken Martin

It'll growl for ever, if you can live with it do so. My diff lost all its oil shortly after getting the car, and after that it growled for many years and thousands of miles, until I swapped the axle for other reasons.
Paul Hunt

Thanks Paul, that makes me feel a lot better.
I seem to remember in the good old bad old days that some shifty UK used car salesmen used to stuff the diff with nylon stockings which would quieten things down a bit. I'm not suggesting that, but would a thicker oil work, or some other additive?
Cheers
Ken Martin

Sawdust was a favorite in the old days. I didn't mean to scare you into replacing the axle assembly. My car came with a very noisy rear axle due the PO not reaalizing that the pinion seal was faulty and leaking oil rather badly. I lived with it for 2 years until I was able to purchase a low milage axle for next to nothing. It has been in the car for 35 years and is still going strong even with the addition of a supercharger. RAY
rjm RAY

Hey Ken,

Try draining, then "flushing" the diff unit with Kerosene or Varsol, after it dries out, refil with good quality, synthetic gear oil and some Lucas Gear oil additive.

As Paul mentioned, the growling will probably last forever without causing any type of catastrophic failure, but this treatment may help with noise reduction. It's worked in the past for me.

JR
JR Ross

No problem Ray, just as long as it doesn't seize up or fall off. Regarding the flushing JR, I have drained the diff in the past and filled it with the Hypoid 90 as called for in the specs which is about as far as you can go. But I was just wondering if Moly-B would do any good. It's supposed to coat everything with molybdenum and reduce friction. Any thoughts?
Cheers
Ken Martin

Hey Ken,

The Moly may be a good additive, but don't mix it with a synthetic product.

JR
JR Ross

Ok, thanks, I might give it a try, unless anybody can think of a reason not to.
Cheers
Ken Martin

This thread was discussed between 03/11/2009 and 05/11/2009

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