MGB: OD Transmission

I have my transmission out of my 77 MGB. I purchased the car for the purposes of restoration but have never driven it. I am wondering if I have an o.d. transmission or a standard one. I have reviewed the archives of this site but find no information as to how to visually identify an od transmission. Can anyone provide a description as to what one might look like? The transmission I have has two electrical plugs on the top. I believe one is for the back up light sensor. I am unsure as to what the purpose of the other.

If you have an OD your gearbox will have a big melon sized ;lump at the back end.
If you don't gave OD it will be pointy.

Great photo of the earlier D type here:


Yours will be a little different in that the solenoid will be internal, but it's the silver lump on the end...

It's huge. You can't miss it. Good luck. RAY

An OD has 4 electrical connections. 2 for reverse lights and 2 for the od..

all '77 gearboxes have both switches...1 for reverse lights the other for vacuum advance limit...look for tag the says: Laycock de Normanville...should be blue in '77

John Twist video 15 MGB here showing an o/d trans and he explains electrical operation

http://www.youtube.com/watch?v=r-WUuz4BzTw&NR=1