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MG MGB GT V8 Factory Originals Technical - sdi rear diff

will the diff from a rover sd1 fit into the axel casing of a MGB to give me the right ratio for the V8 engine
p Dorner

absolutely not!!!
The housing of a SD1 is completely different from a MGB diff housing.I think the best option is to rebuild your standard axle to v8 spec.
Succes

Arno
Arno

Paul,

Find yourself an MGC axle and transplant the 3.07 gears out of it into your B axle.

This seems to be one of the more popular ratios for the V8. I've done this for my project.

Cheers
Simon
Simon Austin

Cheers Simon anyone know where I can get a C axel or just the diff do I also need the shafts as well or are the splines the same
p Dorner

I saw someone advertising new 3.07 set ups, crown wheels etc. in the magazine MG world
Peter

You're welcome, Paul.

All you'll need are the gears. When I got my C axle back, I still had the half-shafts, so as far as I know, the gears bolt right in.

I paid $500 CDN for a complete axle (new gears are horrendously (sp?) expensive, at least over here) and then tried to sell off the half-shafts. Had no offers so I had to scrap them, wire-wheel hubs and all.

After I read your post, out of curiousity, I looked in the book "How to give your MGB V8 power". There's a description on how to convert an SD1 axle for the B but it seems like a lot of work.

Cheers
Simon
Simon Austin

If you want to hunt around for an MGC axle then expect to pay £400 for it - and then have it reconditioned!

Don't forget that the C also had a 3.3 to 1 ratio which gears the B V8 just nicely for a 140mph top speed - the 3.07 gears it for 170!
Chris Betson

If you can find a MGC rear, it will most likely be a wire wheel piece. No need to remove the gears for a transplant to your B rear, just remove the rear hub & all the brake components from both axles, bolt the B stuff onto the wire wheel C axle. Everything is a direct swap with no mods- be sure you swap the brake backing plates.

If you find a 3.07 or 3.331 C, you will be fine using 14" wheels & will have room for much wider tires, up to 205/60/14 on aftermarket or Datsun wheels. If you find a 3.70 C rear, don't despair, it is perfect for 15" wheels using 195/15/65 tires.

Depending, small wheel spacers may be needed to center your wheels using the wire wheel C rear- usually 1/8 to 1/4" on one side 3/8" on the other./

I have run all the above combos on one or more of my cars & they do work. My current roadster has the 3.70 with 195/65/15 Avids with a stock(?) 215, & it is a great combo.
Jim Stuart

Jim,
But what is your OD ratio with that 3.7?
David
David

Jim,
"But what is your OD ratio with that 3.7?"

I hit submit too quickly. What gearbox are you using and what is the 1st gear ratio?
David

If you have an SD1 axle you can have it shortened and modified to fit it to your project. Some twisted halfshafts are reported though; replacement could be expensive.
C ratio is another option.
Last option is to buy a new B axle with the 3.07 ratio. This is now available new from the MGOC. Probably the best option. Expensive - yes, true. But the other options require quite some cash as well. Budget carefully the options that you have. You wouldn't be the first one to think "I can do it cheaper", but ending up spending more than you ever wanted.

Frank
Frank de Groot

David-

My T-5 has a .63 5th gear. The 3.70 rear workd well with the T-5 gears & gives decent accelleration & a usable 1st gear, while 5th give good milage & comfortable crusing at 70 mph. Passing in 5th is the only weak spot & the .73 5th would be better in that regard, but with a bit over 50,000 miles on the car, I would not change anything.

Jim
Jim Stuart

Jim,
Thanks for the info. I guess your 1st is a sub-3.0 gear so that works well. I've run a 3.3 MGC rear for a while with 15 inch wheels. I have a good 3.7 axle sitting in the shop, but I guess the Rover 3.32 1st gear and .79 5th aren't a match made in heaven with that ratio.
David
David

David,

The V8 T-5s have a 2.95 1st gear.
Carl

I went down the shortened SD1 axle route......I do not think the firm who built mine is still in existence, and I have had to replace the SD1 halfshafts with stronger ones, the hubs and drums need drilling for 4 stud, and spring hangers modified, the drums are smaller diameter but deeper, slightly larger brake area, but the SD1 cylinders need replacing with GT ones, its quite a complicated conversion, I did it because I got the axle with the Vitesse I used as a donor, and I also had ideas about changing gear ratios (the SD1 has a choice of 3.9, 3.45,3.08 and 2.84 (which I tried but it is too high,30mph at tickover))

On balance I wish I had used an MGC axle,

Mike
Michael barnfather

This thread was discussed between 08/08/2003 and 14/08/2003

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