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MG MGB Technical - Volvo D-type Overdrive on a three-synchro MGB?

I have a chance to pick up a good condition D-type overdrive that came out of a Volvo. Anybody out there know if its a straighforward swap to replace the one on a 3-synchro MGB?
John Barber

John,

Have a look in the archives, it was a topic discussed few years ago. An easy swap as far I remember.

Cheers,

JGC
Jean Guy Catford

I looked in the archives and found only one under the topic headings. The same question was asked, but no responses.
John Barber

It looks the same, however there are subtle differences, The speedo cable will not fit, unless you get a Volvo end on the B cable, and the ratio will be different. The output flange is different and will not bolt up a B driveshaft. Even though they look the same externally, the sun wheel etc are different. I have used these units for parts to repair a duff B unit. Since you need a mainshaft, remote shifter extension and adapter.. You basically need a OD trans to start with. So they are great for repair parts!!
Marty Schmitz-Hertzberg

The taller .733:1 ratio is what I want. So, I take it that the B output flange will interchange OK? Then change the speedo drive and its ready to go? Nothing more?
John Barber

If I remember the O/P shaft that the flange attaches to is a different diameter, and has a different spline. The flange for a B OD is also a different length than a no OD flange, so even if the splines were the same you need to machine a non OD flange down to work.
The hole in the rear casing where the speedo drive goes in is a different size, so the B unit will not fit.
Even though these units are both D types there are not many exchangeable parts.

If I remember correctly, the splines in the sun wheel etc where the transmission mainshaft goes in are also a different size and type.

The valve housing, brake, springs, pistons etc. and the solenoid are the same as the B unit. So if you have a "duff" B unit, a Volvo unit will give up some spare parts...
Marty Schmitz-Hertzberg

This thread was discussed between 02/03/2007 and 09/03/2007

MG MGB Technical index

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