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MG MGB GT V8 Factory Originals Technical - P6 gearbox in conversion?

Hi folks

I wonder if anyone can help me identify this gearbox. I assumed it was a standard 77 o/d box, then I couldn't find the filler plug. A couple of posters in 'MGB Technical' suggested that it might be the earlier 'box. It does, indeed, have the filler / dipstick on top, but it doesn't look like the drawing in the Haynes BOL. That shows the early gearbox having a pentagonal 'hatch' bolted to the LHS, mine has a rectangular 'hatch' - like the later 'boxes. Also, I have the later type of overdrive.

Anyone know what a P6 box looks like (as that is the likely donor of the motor)?

Cheers,

Nick
Nick Wilson

Nick,
I have a P6 4-speed in my garage that I'd be happy to check out for you. However, I didn't think the P6 3500S came with overdrive...maybe it was an option? Could it be a factory MGBGTV8 box? Personally, if it is a P6 box, I would dump it and get an SD1 5-speed....that's what I'm doing. eMail me with your phone number if you'd like me to describe my P6 box.
Cheers,
Pete
Pete Green

Hi

I was looking at the Moss catalogue last night and noticed that their drawing (page 40) of the later gearbox shows a dipstick (item 128). Now I'm confused.

I'm happy enough with the gearbox. Perhaps if it breaks I'll replace it with a modern 5-speed. The SD1 'box requires some work to the transmission tunnel and a new propshaft. I imagine that modifying the transmission tunnel will result in the centre console (and possibly the carpet) not fitting and will entail a lot of work to get it to look 'right'.

Has anyone any experience of the MGOC kit that uses a Ford Sierra 'box?

Nick
Nick Wilson

Nick

It sounds like you have a standard MGB gear box-the later boxes(67 on) have rectangular plates with MOWOG in the centre. Only the early 3 synchro boxes have the pentagonal side plate(this box was also used in Morris Oxfords etc which came with column changes-this pentagonal plate would then have the levers from the column change acting directly on the selector rails.

Now it is possible that you have a genuine MGB V8 gear box-look underneath the car and check to see if the gearbox is bolted on to the rear of the engine with an adaptor plate-ie a thick metal plate in between the back of the engine and the gearbox.Look also at where the starter motor is bolted to the engine-is it bolted to a lug which appears to be part of the engine-or directly to the plate in between the engine block and the gearbox?
The presence of the adaptor plate means that it is a std MGB box using a V8 conversion co adaptor plate.
No plate -ie the engine bolted directly to the box-and the starter bolted to an engine block lug indicates a genuine MGB V8 box (look after this as it is worth somthing).

With a rectangular plate on the side is almost certainly NOT a P6 box-this has a top plate in cast ally like conventional Ford/Triumph boxes and distingtive cooling fins on the lower surface of the box-the Haynes manual that I have does not mention overdrive either....


Hope this helps

Regards

John Bourke
John Bourke

John,

Thanks. Good info. once again. There is an adaptor plate, so it's a regular MGB 'box. I'm still confused about the filler arrangement. I understood that the 4 synchro 'boxes have a filler in the side, and that the 3 synchro ones have a dipstick / filler in the top. Is it the case that some 4 synchro 'boxes have a dipstick and others have a filler in the side of the case?

Cheers,

Nick

Nick Wilson

Yes Nick, to confirm your suspicions, my '70 "B" came from the works with the dipstick arrangement as in the Mark I B's. A real pain in the rear to check levels! cj
Chris Jones

Nick

I believe that all std MGB V8 and R/B boxes deleted the dipstck/filler and substituted a combined filler /level plug on the side of the gearbox.

The bad news with your adapter plate arrangement is that it usually means that the starter motor lug has been cut off the block-you now cannot use another gearbox without changing the engine block as other gearboxes will not need the adpater plate. Still at least std gear boxes are still reasonably plentiful.

JB
John Bourke

This thread was discussed between 30/08/2000 and 03/09/2000

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