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MG MGB Technical - Transmission whine

Our 79 MGB LE has developed a high pitched whine from either trans or rear end at around 50 mph or 80 kph which then goes away at higher speeds. Annoying to me, car has 60000 miles and is in excellent condition. Oil levels are up. With the top up, as we run the A/C a lot in the summer it really is noticeable.


Kim R
K Rutherford

Does it change as you go from slight accelerate through engine and car revs being balanced to slight decellerate at a constant speed, irrespective of gear? If so it is probably the diff/CW&P. If not is could be wheel bearings, although they usually make a rhythmic drumming that changes with road speed. If it happens at the same revs in more than one gear it is probably gearbox. It was the axle on my car after it lost its oil, they will go on for ever like that (once you fix the leak and put oil back in!) if you don't mind the noise, mine very slowly got quieter and quieter until eventually I changed it for a wire wheel axle as part of another requirement.
Paul Hunt

Paul,
Thanks for your comment, it seems like the noise begins after you have gone through the gears and have settled into 4th or o/d. Perhaps it is not noticeable in lower gears as the engine is building up revs. I tend to rev it up to 4500rpm in lower gears to get going. Car is surprisingly peppy for a later model of only probably 70bhp

Kim R.
K Rutherford

If only in 4th and OD then gearbox. If only in OD then OD.
Paul Hunt

As always thanks for your help Paul.

Kim R.
K Rutherford

Paul,

As an update to my whine in the trans. Had trans oil checked , clean and full. Had my mechanic drain and refill rear end with fresh oil. Whine noticeably less and acceptable with top up. Perhaps the 90 oil had lost a lot of its viscosity !! Also clunk in rear end, which appeared after having it fixed with new pin and washer dissapeared after the u joints were filled with grease. They were noticeably dry. Maybe missed on the last couple of services.


Kim R.
K Rutherford

Interesting oil theory. I'm ashamed to admit that I only changed the gearbox and axle oils for the first time last year, after 20 years and 50k in the roadster and 15 years and 80k in the V8. Made no difference, but then they aren't whining :o) I say 'first time' for the roadster, but when it lost its axle oil I had to put fresh in of course, and it whined afterwards much as it had when it was empty.
Paul Hunt

This thread was discussed between 02/08/2009 and 06/08/2009

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