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MG MGA - Gearbox tightens up.

A fellow MGA owner has asked me a question (via a friend of mine), about his MGAs gearbox which has developed a strange fault since he had it rebuilt relatively recently. I'm not sure how recently.

It is a standard MGA gearbox and apparently, it works just fine when the car is cold, but it tightens up when the car warms up.

I assume he means that the gearshift becomes stiffer to operate when warm.

I am hoping to speak to him directly about the problem sometime over the next few days and I hope to get more information about the problem.
But, in the meantime, I thought I would put the question out to you all to see what your thoughts were.

I have removed and replaced a few gearboxes over the years, but I have to admit that I am not an expert on the internals.

They have too many shafts, whirly bits, springs and detents etc for my liking and I can see me losing too many parts on my garage floor to ever risk attempting to dismantle one.

I will post some more information about the problem as soon as I can.

Cheers
Colyn
Colyn Firth

Hi


Silly response to get it out of the way, is there oil, is there enough, is it the right grade?

Barry
B Bridgens

Barry,
very good response, always my first thought (but still a good thought regardless of that!).
Nigel Atkins

Colyn,
my second thought is, clutch.

Then something about gear lever mechanism.

After that I'd not have a clue.

I don't think it's among the very many problems I've had with a classic (or those that work on them) but I might have forgotten in the mass. If I could remember how all those faults I've had (many repeated) started, developed and were resolved I'd be some sort of expert, but I can't and I'm not, as has been proved manty times here.
Nigel Atkins

I have just received a little more info about this gearbox problem.

Apparently, the main problem is that once the car warms up, it becomes very difficult indeed to select either 1st gear or reverse.

The gearbox was rebuilt a year or so ago and is filled with SAE 20 engine oil and it is filled to the correct level.

My thoughts are that it is sounding like it may be a clutch problem.
Perhaps bleeding or replacing the clutch slave cylinder may be worth looking at to begin with.

I am no expert on gearboxes, but can the gear selector mechanism be in need of lubrication too?

Cheers
Colyn
Colyn Firth

Certainly bleeding the clutch properly shouldn't do any harm and might do some good so is worth a try.

Is 20 SAE a typo and you meant 30 SAE which is more usual, especially this time of year a good 20 filled to the correct level shouldn't make a difference anyway.

AFAIK there's no gear selection lubrication if you mean lever and remote.

Might sound silly but it's free and easy to do and if it makes any difference could lead to what's up - remove the rubber gear lever boot/gaiter and see if that makes any odds.

I'd suggest your friend just asks the builder for ideas as it might be something simple.

Of course you also need to factor in things what is actually meant by tightens up and by how much, also the driver's experience, is he allowing enough for the non-synchro on those gears and or got the revs too high for clean engagement, how long has this been going on, did it suddenly appear, how much use/mileage has the gearbox had since rebuild or how old/mileage/use on the various components of the clutch.

I'm sure a technical type might suggest it might be the wotsit or thingy but as always more details would help which dealing with remote and written only info.
Nigel Atkins

If it only 1st and reverse that are affected it can't be the remote gearshift assembly that is at fault.

Selection of reverse and first gear has no common elements apart from the laygear. This points to wear in all the usual places!

You also don't say what the selection problem is - could it be that he doesn't realise that there is no synchro on either gear and he just needs to be patient and work with the gearbox rather than trying to force it to cooperate? If worn in all the usual places, the solution is a gearbox rebuild..........
Dominic Clancy

Maybe---shot n the dark--it might have oil on the clutch plate, If it has they tend to drag worse as they get hot
Unusual to get engine oil on the plate but if the front seal on the gearbox is leaking oil along the shaft it's possible

Any oil drips from the bellhousing--?
When the gearbox was out, was the spigot bush in the crank replaced--?--If so what type of bush was used
William Revit

This thread was discussed between 06/02/2021 and 09/02/2021

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