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MG MGB Technical - Gearbox whine

Have a really serious constant whinning noise from gearbox - have the carpets out and gearstick rubber off - so can hear everything. Noise comes from just in front of gearstick in the tunnel. Engine and gearbox coming out soon but want to have an idea about the problem...any suggestions?
/Moss
Moss

It sounds like a bearing that is on its way out. The early, '62 to '67, transmissions are notorious for eating up layshaft bearings. RAY
rjm RAY

RJM - he has a '77 car. Did they not improve the laygear to larger shaft and 4 bearings vs 3? But it does sound like layshaft bearings worn.
Art Pearse

Along the lines of gearbox noises Is it absolutely a no no to add a gearbox additive? You know the ones that are PTFE based that bind to all metal surfaces. Mike
J.M. Doust

If there's a fault in the gearbox then so be it and no amount of oil additive is going to disguise this. We need to know a little more to make a diagnosis i.e when is the whine prevalent and can it for instance be heard when the car is stationary if so then it is likely to be layshaft bearings but if not then it could be for some other reason. If the layshaft bearings have expired it will probably be necessary to replace the layshaft the needles and possibly even the laygear if its internal surfaces are damaged. If the whine is present in one particular gear then that gear and possibly the laygear is also damaged and will need replacing. If it is most noticeable in third gear then the cause could be the gearbox rear bearing. My bet however is layshaft bearings so check to see if the noise is present when the car is stationary
Iain MacKintosh

Moss, for what it's worth. If you are going to strip the box down to find the fault, save yourself a lot of time and replace all the bearings, thrust washers, synchro cones and layshaft.

It's not the cheapest way to go, but if the layshaft and/or it's bearings are worn out it is a reasonable assumption that the other bits are worn out.

Spend the money now and save yourself the trouble of removing the box again. I can see no way of assessing if replacing the layshaft (or any other part for that matter) has cured the problem without putting the engine and box back in the car and starting it.

Just my humble opinion. I stripped a ZA Magnette box down to replace the synchro cones, 6 or 7 weeks later I stripped it down again to replace the bearings. It's a hard lesson to learn!

Cheers
Tony
Tony Oliver

Thanks for all suggestions - the noise is constant in all gears and increases/decreases in denstity with speed. That is the whining gets quicker or slower (sort of 'we we we we we we we') When stationary no noise. There is another noise as well when clutch pedal pressed down and let up but I think I know what this is - spigot bearing and worn release bearing...perhaps!
Another thing I have noticed looking down through the tunnel when driving along is the gearbox moves more than I think it should and I can see looking up underneath that the bolts on the gearbox mountings on the crossmemeber are not right - one of them looks as though it is missing
/Moss.
Moss

Moss, if the sound is strictly speed dependent, and is not different in different gears, there is the possibility that it is the rear end transmitting the noise forward.

Charley
C R Huff

Hi,

I second what Charley says. Constant whine , in any gear, that only varies with speed, is diff whine. Mine whinea, I have put the additives in, but still whines. About as bad as my teenage daughter.

Herb
Herb Adler

I did think about the diff, however, the battery cover is off (all carpets/sound proofing and passenger seat is out - all bare metal apart from driver's seat) so I have an open sound source from the rear and have to say the sound is not coming from there. Actually I was gladly surprised at how little noise comes from the diff - not even a clunk as drive is taken up on take off/gear change. It is very much coming from the gearbox - rubber grommet around gearstick and cover is also off.
/Moss
Moss

When rebuilding any model of MG gearbox I would NOT fit a new layshaft without getting it hardness tested. They should be at least 62 rockwell. I have come across early & late shafts that are too soft - ie: 55 to 58 rockwell. I have had two fail after only 1000 miles - 3 & 4 syncro. My tech expert says they are only flame hardened instead of immersion hardened. I now get my own made.
Garth
Garth Bagnall

This thread was discussed between 02/04/2011 and 16/04/2011

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