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MG MGA - Strange Transmission Squeal

This problem surfaced after I drove my car back from the ABFM in Vancouver, BC (this spring up and back in pouring down rain). At it first occurred, in 1st or reverse, as you let out the clutch, just as the car starts to move, there is a rather loud "bad bearing"-sounding squeal from the transmission, the vibration of which can be felt in the shift lever. The mechanic that rebuilt the engine and transmission thinks it's chatter from the throwout bearing, which might be glazed, although that doesn't really explain why it only occurs when the clutch is grabbing but not fully engaged or disengaged. The other, more ominous possibility, he speculates, is that it's the input shaft bearing spinning in its transmission case press-fit recess. (Fix - find another transmission case!) Lately, the sound has begun to occur with more frequency; not just while starting from rest in 1st or reverse, but occasionally when shifting between the higher gears, and a few times when down shifting. Has anybody else encountered this problem? The "bad bearing" sound is very much like what you'd hear from an electric motor with a dirty or dry bearing, sort of a low-pitched squeal (lower than a pig squeal :-) ). Thanks!
David Breneman

Good news is, it'sa a very cheap part. Moss 330-160 Spigot Bushing ($2.95) in the back end of the crankshaft. This bushing carries the front spigot end of the gearbox input shaft. With worn bushing the shaft will orbit inside the bushing. The noise is probably more from the clutch disk rattling around on the splines (or the splined shaft rattling around in the clutch disk) when the clutch is partially engaged.

Bad news is, you have to R&R the engeine to replace the cheap part.
Barney Gaylord

Barney - That's sure good news! But can you tell me if it's "dangerous" to drive the car in this condition? (This is, am I doing damage to other parts?) Having put less that 5,000 miles on it since the rebuild, I'm not relishing pulling it all apart again. I'm getting pretty good at driving it so the noise doesn't happen (ie, letting the engine almost stall when starting from a stop).
David Breneman

David. I had a similar problem with an MGB I purchased and the spigot bushing (also called a pilot bearing) fell out of the crankshaft when the engine was pulled. Shims in the front of the transmission, by the input shaft bearing, were blued and broken. Eventually, there was sufficient movement to produce a pounding sound on start up. I would replace the bad part immediately to prevent damage to the transmission.

Les
Les Bengtson

Les, I'm very surprised that the heat went that far back, are you sure that's where it came from. I've had one fall out of a B as well when I pulled it apart but it caused no problem. This usually only happens when the car is cold and goes away as it heats up and oil comes out of the pores in the Oilite. I would have said to leave it until either the engine or the transmission has to come out next.
Iain MacKintosh

Iain. Having only a single experience, and that on a car that I had just purchased, I do not know. What I found when I pulled the engine and tranny was that the spigot bushing was loose in the rear of the crankshaft (remove with fingers), showed external scoring and internal scoring. It was the correct bushing for that engine.

The first mostion shaft could be moved, upwards and downwards,a noticable amount. When I removed the front cover, two of the thinner bearings showed heat bluing and one was in three pieces. Heat bluing could have been from a piece becoming jambed into another piece causing a binding situation with resulting heating.

I hate to base a recommendation on a single instance. But, if I ever hear the squealing again, I am going to immediately pull the engine and tranny and correct the problem. If others have had a similar problem, and have let it go for an extended period without causing other problems, it would be useful to know and would help all of us in our decision making.

Les
Les Bengtson

David, -- It's not dangerous, and it may run a long time without doing any significant damege, but it will only get worse with time. Gotta fix it sometime, so your earliest possible convenience is probably best.
Barney Gaylord

Could it be the Clutch Throwout Bearing? Is it WORSE when you PUSH IN THE CLUTCH? My M.G. midget 1275 squealed like a stuck pig & it was the Throwout Bearing. Unfortunately I waited too long replacing it and IT ATE UP THE CLUTCH COVER ASSEMBLY! Not all that bad, because you should ALWAYS replace Clutch Cover, Friction Plate, AND Throwout Beasring ALL THREE on a Clutch Overhaul anyhow! DIDN'T GET MY $35 REFUND ON THE OLD CLUTCH COVER ASSEMBLY - NOT REBUILDABLE!
OLD BILL-67

Bill -

The sound is not there with the clutch pedal fully depressed nor fully released. Only as the clutch is slipping, and usually only in the high-ratio gears, 1st and reverse; although now it is occasionally happening on higher gear shifts as well.

David Breneman

This thread was discussed between 28/08/2005 and 03/09/2005

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