MGB Overdrive

[philipandrewdavid]

I need to replace the gearbox on my 68 traveller and would like a 5th gear but dont really want a type 9 conversion. Is it possible to fit the MGB overdrive box?

[chesney]

It is possible to fit the MGB engine and box into a Minor..
Not knowing the MGB box I'd assume it has a completely different bellhousing system and won't fit the A series. Of course, anything (in reason) will fit but this is probably not the best option..

[bmcecosse]

At the risk of being shot down.........my advice is to simply fit a lower ratio final drive in the axle, and of course a good working standard gearbox in your case. It's easy and relatively inexpensive to fit a different final drive, and it will 'always' hold value whatever you have to pay for it. My 3.7 ratio cost me £70 a couple of years ago - they now seem to change hands at ~ £200. But the more common 3.9 ratio is more affordable, and probably better suited to a standard 1098 engine anyway! My mate has a spare o/d MGB gearbox lying around - it's surprisingly small and while the bell housing is of course slightly larger, it is similar shape to an A series bellhousing. However - mating a B box to an A engine is not something I have tried, but as above -I dare say it's not impossible if you have the resources !!

[brucek]

Check this link for a rebuild that has done the MGB engine/box swap

http://www.mmoc.org.uk/viewtopic.php?f= ... at#p465195

[charlie_morris_minor]

looking at the pictures of the gearbox, it does indeed look small especially around the bellhousing area.

if i were going to look at this conversion i would think about changing the backplate on the engine as is done when mating the marina engine to the minor gearbox as opposed to changing the bellhousing as done with the type 9 conversions.

It would be relativly cheap (but time consuming) to make something out of mdf / ply wood to trial fit the engine and box together and then fit it to the car, you could then satisfy your self that they fit and that the gear leaver is in the correct place for you when driving before you make it in metal. this would leave one big question about which clutch to use?

other problems / expenses could / would include the clutch actuation mechanism, propshaft, gearbox support and i would plan that the gearbox tunnel cover would need modification which could lead to new carpets if the old ones nolonger fit.

one other thing to consider, I do not know the gear ratios in the mgb box and how they would suit the minor given that the box is designed for a larger torquer engine?

[daveyl]

Out of curiosity, does anyone know if you can fit an MGB geabox to a 'Marina 1800', without changing the Marina engine back-plate?

[Matt]

Would you get away with a marina 1300 backplate?

[philipandrewdavid]

Many thanks for all the advice, I think i'm going to give it a go and report back. This may take some time as i have Austins A35, A40, A55mk2 and A60 to contend with as well as the new Morris!

[kennatt]

Out of curiosity, does anyone know if you can fit an MGB geabox to a 'Marina 1800', without changing the Marina engine back-plate?

Was common the otherway ie marina engine into mgb with mgb box,done three or four myself. The differences are ,spiggot bush in marina is thicker,cos the ist motion shaft is thinner on the marina so will need charging to suit mg box. So from memory,the mgb box will fit the marina with the correct spigot bush.Ie mgb bush into the marina engine to accomadate the thicker input shaft of the mg.box.

[philipandrewdavid]

Charlie, as i undestand the final drive for the sierra type 9 is exactly the same as overdrive 4th on the mgb box. I assume the spacings are different but then with the overdrive one has the choice of 6 ratios as opposed to the type 9's 5 so i guess, and i'm only guessing it should be ok.