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MG Midget and Sprite Technical - third gear problem

So, After spending forever bleeding the clutch we finally got out for a run today. However, after a few miles of 'spirited' acceleration, I eased off and found that third gear was incredible noisy. Kind of a rattle but not as metallic as that suggests. Only get it in third. the rest of the gears are only as noisy as they're supposed to be. Needless to say we turned back straightaway.
Any thoughts?

Graeme
graeme jackson

forgot to say - there doesn't seem to be any loss of 'pull' - just sounds like it's about to explode.
graeme jackson

Lay gear shaft....or bearing excessive wear. Better to look at it now before you chip all the gears into oblivion. Thats my guess... You would be surprised how worn it can be and still work right before devistation. Cheap to fix parts wise. Labor intensive.
Steven Devine

Thanks steven. The very thought of stripping a gearbox has me more worried than a visit to the mother-in-law :-(
graeme jackson

It could be excessive play in bearings, worn layshaft, or even a broken tooth.

Only one way to find out.

I find A-series gearboxes very satisfying to work on.
Dave O'Neill2

Ok. So I've opted for a replacement gearbox that the seller tells me has no broken or chipped teeth and all the gears change and run ok. *
Question - I'll probably replace the front cover and side cover gaskets while I have the box on the bench.
Do any 'sprung' parts rely on the covers being in place? i.e. will I be sending ballbearings all over the garage if I take the covers off too quickly?

* I was the only bidder on evilbay so got it at a good price. Hopefully it'll be in good enough condition to last the car out but I'll be happy if it lasts this season so I can get my own box rebuilt (or exchange it for a fully rebuilt one.
graeme jackson

the side cover keeps a couple of springs and detent balls in place, so lay it on its side such that the cover is removed vertically upwards. Undo all the retaining nuts halfway first to release the spring tension and then nothing will leap out.
David Smith

Just be careful that the springs stay where they are and don't come off with the cover, only to lose their grip and then fall on the floor.
Dave O'Neill2

Yup, or fall into the gear box.

Charley
C R Huff

Charley

It's funny that you should say that.

I took the side cover off a 3-synchro MGB 'box recently and one of the spring-washers fell into the gearbox.

Fortunately, I managed to fish it out with a magnet!
Dave O'Neill2

Handy that it was a ferrous part, Dave. It could be an argument for NOT laying the box on its side to pull the side cover.

Charley
C R Huff

This thread was discussed between 21/04/2014 and 29/04/2014

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