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MG MGA - Strange noise in 3rd gear

Hi guys,
A strange rattling noise has suddeenly appeard when I put her in 3rd gear, all other gears ok. 1955 roadster with original gearbox. Any ideas what this may be?

Thanks

Arty
AR Terry

Lots of posts about strange noises. Is it possible to attach a .mp3 file so we can hear them?
Art Pearse

Do you have a wooden knob on the shift lever? I am told that they can make a rattle noise.
Ed Bell

Ed, that would rattle in all gears.
Art Pearse

A broken tooth on 3rd gear will make a loud tick with each revolution, louder under load, less loud with less throttle, frequency proportional to ground speed and equal to prop shaft speed. One missing tooth might make no noise. Two missing teeth will definitely click loudly. Three missing teeth will make it lock up or will refuse engagement of 3rd gear when in motion.

To check this you need to remove the gearbox side cover to count gear teeth. That unfortunately requires removal of engine and gearbox, or disassembly of interior to remove floor and transmission tunnel. If there is a broken gear tooth it requires complete disassembly of the gearbox to replace the bad part (3rd gear or lay gear).
Barney Gaylord

Thanks to all for your suggestions. Bit the bullet and pulled the engine and gearbox. Sitting in the bottom was the front thrust washer from the lay gear, couldnt believe it! bit chewed up but cant see any damage to the gears. Hey ho got to put it all together now.

Best regards

Arty
AR Terry

So, did the washer drop off the layshaft during assembly, or did it wear out and drop off? Very strange either way that you did not wreck the box!
Art Pearse

Was a bit of a head scratcher to figure out where it came from as its impossible for it to come off so I can only assume I missed putting it on correctly last time I had the box apart about 3 years ago. It must have just sat quietly doing nothing until something disturbed it and threw it into play with all the moving parts. As you say it was a miracle the box wasnt wrecked, glad I stopped driving it.

Regards
Arty
AR Terry

This thread was discussed between 29/04/2011 and 04/05/2011

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