MG-Cars.net

Welcome to our resource for MG Car Information.

Recommendations

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGA - Gearbox whine

Hello all,

I have developed a high pitch whine/grinding sound at speed under load. Definately sounds like metal rubbing metal. It sounds like it is coming from the gearbox or clutch area because it is loudest when I stick my head under the dash and you cannot hear it under the hood with the car stationary.

The sound is most audible at 3500 RPM and above and doesn't start until 3000. It starts when the accelerator is depressed and will stop and start, but it will always stop if the accelerator is released or eased up on. The car must be under load to get the noise to start.

The car has also begun to leak more oil than normal from the cotter pin in the bell housing but I'm having trouble determining if this is actually the leak point or not.

I did discover a leaky valve cover and have fixed that. That may have been the cause of most of the oil.

So far here is what I've done.

Changed engine oil (no sign of metal)
Changed gearbox oil (no sign of metal)
Checked plugs #1 and #2 are running a little rich but not bad
Checked compression, engine warm throttle wide open it is:

#1 135 psi
#2 130 psi
#3 130 psi
#4 135 psi

Adjusted valves (none were really out)
Replaced valve cover gasket
Oil pressure at speed is 70 - 80 lbs

I thought I might drive her for awhile and see if I've stopped the oil leak or not, but any ideas on what this sound might be? It is quite troubling and I've never heard a noise like this in all the years I've driven the car. It is definately not normal I just don't know where to look at this point.

Thanks,
Christopher
Christopher Wilson

Christopher, assuming that you are talking top gear only?
If so, then there is only one loaded area that I can think of to make such a noise and it is the crown wheel / pinion. However what you describe is not characteristic of that problem, which is usually a moaning sound all the time.
If it is in the lower gears, I would suspect worn layshaft bearings. These are not loaded in top gear, just spinning, but I suppose could be noisy.
Could also be the clutch release forks rubbing on the input shaft if the bushing is worn, but I don't know why that would depend on speed or load.
I vote for layshaft bearings.
Art Pearse

Well fellas this will be a project for early winter.

After driving the car still leaks a little. About 1/4 ounce after a drive.

Art, the noise is in all gears under load. I think you are right about the layshaft bearings.

I used some UV dye and determined the leak is coming from the tranny. Not terrible and it must be the front seal.

Thanks for the input.

Christopher
Christopher Wilson

Christoper, how much oil is left in the gearbox after all these 1/4 oz leaks?
Art Pearse

Right now over 2.25 quarts but that is because I just filled it the other day. I am going out of town for a few days but when I get back I have a 100 mile round trip planned and I can fill before I leave and check at the halfway and then when home and probably pin point at what rate the oil is leaking out.
Christopher Wilson

This thread was discussed between 08/09/2010 and 12/09/2010

MG MGA index

This thread is from the archive. The Live MG MGA BBS is active now.