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MG MGB GT V8 Factory Originals Technical - Gearbox identification

Can anyone tell me what is the difference between a standard MGB gearbox and the version fitted to the factory V8 cars? I have a roadster which was the subject of a 1986 V8 engine conversion, and it appears to have the original box. However if there is a small chance the box is a factory car model I would like to know because I understand the lubricant requirement is qiute different. How can I be sure exactly what it is I have?
Steve

I am sure you will attract more knowledgeable replies than mine, but I have a factory V8 gearbox in my 1963 conversion. The main difference is the bell housing. If this mates directly to your motor then you more than likely have a factory V8 gearbox. If there is an adaptor plate you may have a 4 cylinder gear box which utilises the flywheel from the 4 cylinder motor and an alternative way of mounting the starter motor as was done by Costello.

Having said that I have a factory gearbox, I believe the internals in my case are from a 4 cylinder and would be interested to hear all the actual differences internally for a real V8. For example the lay gear is different in a totally original V8 gearbox.

cheers
Ian Buckley

You're correct, the gearing is different, closer ratio I believe, and the original V8 boxes had a different bellhousing that was integral to the gearbox like the 4 cyl.
Jake

Clausager says the basic design was the same, but with closer ratios, a higher first gear, and a completely different (unique to the V8) casing incorporating the bell-housing and space for the larger clutch. Also apart from a few very early cars the V8 only had overdrive on top whereas UK 4-cylinder cars always had it on 3rd and 4th.

4-cylinder cars use engine oil in the gearbox, V8s use back axle oil. This was more to do with the increased stresses than anything else so maybe a V8 engine with a 4-cylinder box should make the same change.
Paul Hunt

MGB 3 syncro
Overdrive: 0.802
Top: 1.000
Third o/d: 1.10
Third: 1.374
Second: 2.214
First: 3.640
Reverse: 4.760


MGB 4 syncro
Overdrive: 0.820
Top: 1.000
Third o/d: 1.133
Third: 1.382
Second: 2.2167
First: 3.333
Reverse: 3.095

MGBGTV8
Overdrive: 0.820
Top: 1.000
Third: 1.259
Second: 1.974
First: 3.138
Reverse: 2.819

MGC
Overdrive: 0.820
Top: 1.000
Third o/d: 1.072
Third: 1.307
Second: 2.058
First: 2.98
Reverse: 2.679

Geoff
Geoff King

This thread was discussed between 30/05/2003 and 04/06/2003

MG MGB GT V8 Factory Originals Technical index

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