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MG MGB GT V8 Factory Originals Technical - Rover V8 with standard gearbox


It'is possible to use the gearbox and rear axle of the standard MG B 1.8L with a Range Rover 3.5L (128BHp model) engine?

Greg Grégory

Yes, it's possible but the gearbox might not last too long. On the factory cars they used the original MG gearbox, but toughened up some of the components. There are still some issues with weakness in the 'box with these, so a standard 'box might be a bit fragile. The later Salisbury axle (1965 on) will take the extra torque easily, but the ratio of the standard axle is really too low for a largish V8. You would find that 1st and possibly 2nd gear were really not much use, and that fuel economy at motorway speeds was poor due to the high revs needed.

Mike Howlett

Tank's for your informations
Greg Grégory


Ingemar Lindblad

supra gearbox (0.78 fifth gear) with a bell housing from Dellow automotive in Sydney. He ships world wide. I'm using a standard back axle and find this combo' just fine. 2600 revs at 100km/hr, which is right about where the torque/power curve begins to flatten out with a EFI 3.9 motor and it is running most efficiently. At 110km/hr, with the top down, over 8 hours, I got little over 10 kilometers per litre. I don't use oxygen sensors in the exhaust, however if someone did they should be able to improve the milage still further.
The small light (and very strong) toyota supra box fits into the MGB tunnel with no alterations needed. With other boxes you need to cut and weld.
In Australian $ Dellow wants around $500 for the basic bell housing, fork and spigot bush. You can then spend another $400 on clutch etc, but you would be better getting this elsewhere. For example a one inch rover slave works much better than the supra.

Greg, just for information purposes...I am running a '63 buick 215 (HO) with the 3.9 factory rear end in my mgb.
I have a '92 Z28 T5 with the .63 5th gear ratio. I routinely get 30 mpg on interstate driving. Although 1st gear is seldom used, I really like this setup as it gives me brisk acceleration through the gears and relaxed highway driving.
Mike Maloney

A lot of the early V8 conversionsin the UK used the original gearbox without too many problems. A special adaptor plate was made by the V8 conversion company in Kent. These are no longer available, but I do have one available(plus machined flywheel, clutch etc) if you decide to go this route.The mgb flywheel is machined to take MGC cover plate and MGBV8 driven plate. 12mm is removed from the first motion shaft, the MGB starter motor is mounted on the adaptor plate so the originl mounting on the engine is removed. a section of the bellhousing has to be removed to clear the repositioned starter.I can send a copy of the original fitting instructions if you wish!Cheers, Dave
DM Gibson

Thank's all,

Dave I'm interested by your instructions, can you send me a copy on my email please :

Greg Grégory


I have an ex-Costello (I think) Rover V8 engine/ MGB gearbox combination which I'm using in my MGBGT . I would be very interested to read the fitting instructions for my combination as an aid to maintenance if necessary.

If you could please send me a copy to I'd be very grateful.

Many thanks.

P L Hills

I used the standard gearbox with my first SD1 engine.
It was totally standard but still managed to shred the teeth on 2nd gear twice.
from my experience the box is just not strong enough.


This thread was discussed between 07/05/2007 and 17/05/2007

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