mgb gt 3 syncro to 4 syncro conversion, help please.

[andrew tolley]

hi to all the mgb experts out there, i have a problem please help if you can, ive recently purchased a 1967 mgb gt mk1 with a 3 syncro non overdrive gearbox, this gearbox makes a very strange nasty noise in first gear and also does not like going into second gear while moving, my question is will the 4 syncro non overdrive gearbox gearbox fit my car and is it a straight swap, if not what parts do i need to fit it?
thanks in advance
andrew.

[wildoliver]

No won't fit in the tunnel.

Your car doesn't make a nasty sound in first, it is the sound a straight cut gear should make (assuming it is a whine, if it is knocking or squealing there is an issue) it should slip in to second but second synchro does take hammer on these gearboxes as if you drive them properly you lean on second synchro to slip in to first when still rolling. However if it is not crunching in to second on a positive but slow shift then there is nowt wrong with it.

Trying to change a 3 synchro MGB to 4 is nothing short of madness as it will result in body modifications and leave you with a car worth far less than a standard model. If you don't like it sell it and buy a later model, far better long term plan.

[andrew tolley]

hi wildoliver thanks for the response, first gear engages fine but when driving sounds like a flapping/knocking noise, second gear crunches unless car as almost stopped when engaged, on ebay there are rebuild kits for the 3 syncro gearboxs, two different kits, one for 3 hole and one for 4 hole do you know which kit is for my gearbox 3 or 4 hole?
thanks andrew.

[wildoliver]

In theory 4 hole provided it hasn't been swapped over the years. That said the 3 and 4 hole side of things relates to the layshaft, and if it isn't jumping out of gear then the layshaft and bearings should be fine anyway, so if you did order the wrong kit it wouldn't be the end of the world just don't fit the layshaft bearings.

I've never had a 3 and 4 hole box stripped (mainly because it is a once in a blue moon job rebuilding a 3 synchro box) together to see if the layshafts are interchangeable.

[andrew tolley]

hi wildoliver thanks for the response.
andrew.

[Huntsman]

As its a non overdrive car, have you considered a five speed conversion with a ford gearbox?

See hi-gear engineering. They do a conversion kit for your car and local scrap yard with provide 5 speed box.

[andrew tolley]

hi huntsman that sounds good i will take a look.
andrew.