Steering, Suspension, & Brakes

tips, technology, tools and techniques related to non-driveline mechanical components

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mabie1978
Michelle Pierce
Elyria, OH
(111 posts)

Registered:
08/25/2008 07:47PM

Main British Car:
1978 MGB 3.5 Rover V8

Racing diff?
Posted by: mabie1978
Date: June 11, 2012 11:48AM

A guy fairly close to me has a racing differential for sale, he doesn't know much about it since he has had it for years and just got the info from the guy he bought the parts from. He said it is a low gear but he can't remember exactly what it is. Said he was told it would be great for track driving on a roadcourse. Is this anything I might want to pick up? My car is already geared low and it's favorite gear is 4th of 5th. Just curious, I have done some searches and can't really find much info, if it was a limited slip I would grab it but he can't remember if it is. Any thoughts?


mgb260
Jim Nichols
Sequim,WA
(2003 posts)

Registered:
02/29/2008 08:29PM

Main British Car:
1973 MGB roadster 260 Ford V8

Re: Racing diff?
Posted by: mgb260
Date: June 11, 2012 12:52PM

Michelle, For the street you want higher gears,not lower.Lower gears will allow faster acceleration but lower top speed. Confusing but lower are higher numerically(stock MGB 3.91-lower 4.11). MGC 3.31 would be ideal if you could find it. Lots of people change out the rear end for Ford or Chevy 3.23-3.45 gears. Do you have the V8 T5 or V6. The V8 ratios are fine with the stock rear gears. The V6 ratios you need higher gears like the 3.23-3.45.


mabie1978
Michelle Pierce
Elyria, OH
(111 posts)

Registered:
08/25/2008 07:47PM

Main British Car:
1978 MGB 3.5 Rover V8

Re: Racing diff?
Posted by: mabie1978
Date: June 11, 2012 01:40PM

Jim, I have a v8 T5 in it now. This guy just has the pumpkin which made me hope it was a limited slip but I have a feeling it wasn't.


Moderator
Curtis Jacobson
Portland Oregon
(4411 posts)

Registered:
10/12/2007 02:16AM

Main British Car:
71 MGBGT, Buick 215

authors avatar
Re: Racing diff?
Posted by: Moderator
Date: June 11, 2012 03:25PM

Quote:
A guy fairly close to me has a racing differential for sale...

Likely problem: most people who race MGBs retrofit the earlier "banjo style" rear axles for which lower ratios and better differentials are readily available. The banjo housings are also significantly lighter than the later cast iron "Salisbury" housings. Diffs and gears for a banjo axle won't fit in a Salisbury housing, so I doubt you can use the parts he has on offer.


WernerVC
Werner Van Clapdurp
Lynchburg, Va
(93 posts)

Registered:
09/06/2009 12:56PM

Main British Car:
MGB 1977 Rover 3.5

Re: Racing diff?
Posted by: WernerVC
Date: June 12, 2012 11:10AM

Michelle,
On your question if the diff is a limited slip diff you can try the following. Turn on one output shaft and when the other output shaft turns in the same direction than it is a limited slip diff.
Hope this helps.
Werner


mabie1978
Michelle Pierce
Elyria, OH
(111 posts)

Registered:
08/25/2008 07:47PM

Main British Car:
1978 MGB 3.5 Rover V8

Re: Racing diff?
Posted by: mabie1978
Date: June 19, 2012 09:48AM

Curtis, can you tell the difference in the pumpkin based on looking at the exterior housing or is it internal only ?


Moderator
Curtis Jacobson
Portland Oregon
(4411 posts)

Registered:
10/12/2007 02:16AM

Main British Car:
71 MGBGT, Buick 215

authors avatar
Re: Racing diff?
Posted by: Moderator
Date: June 19, 2012 12:08PM

A Salisbury axle looks like this:
http://www.britishv8.org/MG/MikeAlexander/MikeAlexander-KV.jpg
Cast iron center section, with welded-on round tubes extending outward toward the wheels. The gears and differential are removed through the back after removal of a bolted-on rear cover.

A banjo axle looks like this:
http://www.britishracecar.com/MikeKusch-MGB/MikeKusch-MG-MGB-DF.jpg
The axle housing is fabricated out of stamped steel parts, not castings and not tubes. The gears and differential are removed from the front, with their aluminum carrier.

From what I can tell, pretty nearly all vintage racers use the banjo style housing. I think most SCCA racers have used the banjo axle too, but the percentage might not be quite so high. (Actually, to split hairs, a fair number of racers make hybrid axles that combine the center of a banjo axle with the hub bearings of a Salisbury to get some of that strength/safety.)



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