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MG MGA - Gearbox noise

I read all I could find and none seemed to be my exact noise situation. A couple months ago, when accelerating during a long left turn I heard a random tinging sound which sounded to be somewhere under my heater box. I though something was simply rattling. I could not find anything loose so I tied down or buffered everything I could put my hands on. The noise began showing up anytime and got worse. No noise with the clutch in, coasting or in neutral.

I put about 80 miles a week on it and it has gone from a tinkling sound to a shaken can of marbles in 2nd and 3rd gear and is random. I would have thought gearbox teeth if it happened all at once. I'm not even sure it is the gearbox, I can not feel it in the shifter and it runs as smooth as before.
Suggestions?
Thanks,
Randy
R Palsgrove

I had a rattling sound in mine which appeared to be coming from the same general direction as yours and which stopped when the clutch was depressed.

It turned out to be slop in the clutch withdrawal lever. The phosphor bronze bush had worn and so had the lever bolt. Also, and probably because of the wear in these two, the spigots on the release bearing had worn oval. I had to replace all three items to cure it............... Mike
m.j. moore

Depending on mileage, worn layshaft is a good bet. How many miles on the box?
Art Pearse

Randy,
You might try removing the drive shaft, starting the engine and running it thru the gears just to hear what it does. Granted, it's not loaded but it's a fairly easy thing to try. You might want to get a stethascope and give a listen. Put it in neutral and spin the output shaft by hand. With the dive shaft out, support the axle housing and spin the rear end. Check for slop at the differential input shaft. You might want to remove the rear brake drums and check for loose hardware and slop in the axle bearings. Also, check for broken fan blades and bad generator bearings. That should narrow it down.
Good luck,
GTF
G T Foster

Oh, shut the engine off when you put it in neutral to check the output shaft. :)
GTF
G T Foster

Mike, were you getting clutch chatter before the noise?
R Palsgrove

As far as I can remember (25 years ago!) there was no problem (or noise) with the clutch itself and it didn't need replacing.

It might be worth your while to get under the car and try wiggling the end of the clutch withdrawal lever to check for any sideways play. If there isn't any you could quickly rule it out as a cause of the rattle............Mike
m.j. moore

Got play about 1/4" side to side. Should there be zero?
R Palsgrove

If the play is plus or minus 1/8" it's probably not too bad. Maybe two or three times what it would have been originally. To give you an idea plus or minus 1/4" would be enough for the inside edge of the release bearing hole (1.5" diam.) to hit the drive shaft (1" diam.) and that would probably cause a loud knock! If you eventually remove the gearbox it would be worth replacing the bush and bolt as they are relatively cheap.

The rattle might be due to a loose release bearing; maybe a spigot spring broken or even missing.

However I'm going off the idea that your noise is due to the clutch release mechanism because you say the rattle is not audible when in neutral whereas mine was loudest when coasting/in neutral. Sorry I can't be more help...............Mike




m.j. moore

I dropped the front of the prop shaft as suggested and there was no rattling noise but I'm not sure what that tells me.

Very little slop between the prop and rear. All brake parts good.

The marble in a can noise does get a bit more intense as the engine revs but does not rise evenly with the rpm of the engine.
R Palsgrove

If there is no bad noise with the prop shaft disconnected, and I assume you went through all the gears (?) then it sounds like it is not a gearbox noise at all!
Art Pearse

Randy,
You say "The marble in a can noise does get a bit more intense as the engine revs but does not rise evenly with the rpm of the engine."
Do you mean you are hearing the same noise, just not as bad? If so, I would suspect a transmission problem. Have you turned the output flange of the transmission by hand? If so, what did you feel? Unfortunately, this can only be done with the tranny in neutral, so it only checks a few things.
Good luck,
GTF
G T Foster

The tingling noise could also be caused by the starter bendix. They will clink against the teeth on the flywheel and make all sorts of tingling sounds.
Sandy
ss sanders

This thread was discussed between 05/01/2011 and 14/01/2011

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