Welcome to our Site for MG, Triumph and Austin-Healey Car Information.


MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGB GT V8 Factory Originals Technical - Swap gearbox?

Hi all,

The 4+OD from my original B GT V8 was recently overhauled, but not to satisfactory result. It still jumps out of third gear occasionally. Of course this is guaranteed work, so the gearbox has to come out again. But...I could also drop in a real five speeder. The engine produces around 170 bhp at wheels, so I wonder if I should do this. Several people pointed out that originality is a good thing, and that the gearbox is in fact strong enough.
Being an everyday driver, I don't want the gearbox overhauled every couple of years.
So what to do, and what are the costs and parts availability of the different options?
I was thinking along the line of:
- SD1 gearbox (belhousing scarce)
- BW T5 (expensive box + even more expensive bellhousing)
- Toyota Supra (don't know what importing/shipment will cost me)
- other options?

Frank de Groot

How about the Ford Sierra 5-speed? Fits the MGB very well and has good ratios. Also plenty of them about.
Mike Howlett


Call hofman in Leek he has some used SD1's 5-speed in stock for around 400,=/500,=.(compleet with bellhouse) Be sure to ask for Hofman himself. phone 0594-516604 or Otherwise Rene Winters at

Guido Smit

Thanks Mike and Guido. The current offer from Imparts (the ones who also did the gearbox) is that the 4+OD will be overhauled again for free. Sounds good, but it is perhaps a better idea to put a five speeder in? I wonder if Sierra 5 speeder will be up to the torque?

Frank de Groot

Hi Frank
The Sierra gearbox will only handle 175hp and a similar torque at best. The box to go for the T5 or Rover box but both of these might work out costly for you. The Supra box is worth a look as not many people want them, so they are cheaper than the alternatives plus they will handle all the power and torque you would reasonably throw at it.

It's worth considering the Range Rover five speed box - it fits in very easily, and is not expensive.

Jon Eales and other specialists often have new and/or reconditioned boxes available.

John Eales
Claybrook Mill
Frolesworth Lane
Claybrook Magna
Leicestershire LE17 5DB

Telephone 01455 202909

Best time to telephone 18:00 local.

Safety Fast

Nigel Steward


Where would you buy a Supra gearbox? Any addresses? I have a distinct liking for Japanese quality, but I wonder how to fit the W58 to my Rover V8. I know there are kits from New Zealand/Australia, but how do you do it in the US?
Nigel, thanks for the address. I am going to try and see how much a good five speed Rover box will set me back.

Frank de Groot


Also try Terry Brown SD1 specialist. Has Tim decided against making Costello box?


Hi Frank
The Supra box is easy to get here in the USA as they sold a great many here. They were not that popular in Europe so you might have a little more difficulty finding one there. They are available in the breakers yards or via the transmission specialists. Try looking in the Exchange and Mart magazine.
The only real special part you need is the bellhousing, they can be obtained in NZ or Aus at reasonable money and the shipping costs are not at all bad! In fact when i was in the tranny business i made several 5 speed conversions for various vehicles and after doing a lot of searching i found out that i could have castings made in the far east and Austrailia and shipped to the USA cheaper than i could get one cast over here.
I hope this helps

Tim has had plans, but that's about it. The plans for the Costello box have been postponed indefinately. Different people have told me of too. The quality is very bad and the parts are not from a know source. And what's the point in building a gearbox when there are so many good alternatives?

John, thanks! I have an address for people that do these bellhousings and several small parts. Prices are not that bad at all. Do you know some people who sell Supra gearboxes and that you can trust? Trust is a problem, so if you could recommend somebody (perhaps by mail) I would be delighted. Thanks!

Frank de Groot

This thread was discussed between 07/06/2002 and 10/06/2002

MG MGB GT V8 Factory Originals Technical index

This thread is from the archives. Join the live MG MGB GT V8 Factory Originals Technical BBS now