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MG MGB GT V8 Factory Originals Technical - capri3.07 axle or mgb3.9

i am restoring and converting my roadster to v8 power.The engine and box have been rebuilt 3.5 and 5 speed lt77 box. Everything is going well except for the rear axle. I have a standard B recon axle , a tatty standard standard B axle and a capri 3.0 litre axle which seems in good condition. Has anyone fitted a capri axle out there and could it be made to fit i can see the obvious width difference.Could i use the standard B axle or has any one got a good used 3.07 diff cheap(you never Know)Cheers Paul
p stanford

Hello Paul
Ive got a new 3.07 crownwheel and pinnion that I bought and never used. Bought it from MGOC about 5yrs ago for around 350 quid. If you are interested make me an offer. v8mg@blueyonder.co.uk.

Cheers

Mark
Mark

I've been using a standard MGB back axle with my 3.9 conversion. The salsbury one is more than strong enough. The very early bango style diff's are reported to be not strong enough. I did use a thicker tail shaft though.
Peter

Worth bearing in mind that MGB Hive sell v8 axle's on an exchange basis for £550...
Gavin Jewkes

hmm, you could always fit a Jag IRS. You can pick them up for buttons (few hundred quid), recon the bits you need (brakes etc) and get a custom cage. I worked out it would cost me under a grand all in if I did some of the hard work - maybe a bit more that what you wanted to pay, but you'd end up with a rear end capable of taking 600bhp, coilovers and huge inboard brakes :)

If you're gonna pay £550 for a MGB Hive axel it's probably worth considering . . .

Other than that, I'm using a Rover SD1 rear axel, which (hopefully) is enough to support the 300bhp I'm planning on shifting through it :)
OT Hayter

Thanks for the help.I cant afford the £550 for the axle .What would the v8 run like with a 3.9 diff. I know it would pull away fast but what about top end and more importantly Cruising speeds.The capri axle is not a good idea then??
p stanford

The capri axle is miles to wide,and I would say only about as tough as a MGB,speaking of which I broke mine! the planet gears/shaft snapped in half.
I got an eight inch Ford housing from the Currie enterprises USA, they can supply and narrow a rust free housing with new tubes very cheap,posted to the UK ,I then got bulletproof axles made to my spec from Moser USA and had them sent to my hotel on a holiday to Florida,I took them home in my hand luggage! Ford Sierra discs and calipers can be made to fit on the rear with redrilling the discs and simple 8mm brackets bolted to the 8" flange.
Dave Lowe

The SD1 will need some decent halfshafts.

I would try to stick to B axle in view of potential of DVLA changing rules re radically modified vehicles.
Paul

I enjoy the sporty responce with the 3.9 diff'.
How well the 3.9 diff works for you is going to depend on your set up. How much power and what gear ratios you are using. For comparison, I am using the 3.9 diff with the 3.9 V8 that is pretty well standard at around 180 or 190 BHP (I would guess). I am also using a supra W58 gear box. 1st 3.28, 2nd 1.89, 3rd 1.27, 4th 1, 5th 0.78
I can (and usually do) take off from stationary in second gear with heaps of accelleration which will take me up to at least 70 km/hr with out changing. Other cars run out of zing at about half that.
I like that First gear for slow traffic & car parks etc., it's about right. Having to constantly slide the clutch would be unpleasant. The 0.78 seems to work well at high speed, with plenty of zing. At the speed limit the engine is reving around 2600-2700 rpm which is just about where the engine is working at its most efficient, lots of throttle response. I have some doubts that I could improve the economy by going to a lower ratio because at around 2000rpm the engine would be operating less efficiently. At least thats my excuse, I did not put a V8 in an MGB for reasons of economy!. Although the economy is infact suprisingly good. Not much different from the old 1800 with its thirsty SU's. The EFI and fact that the car is about 30 odd Kg lighter makes a difference.I suggest you try it with the diff you've got and see for yourself. You can always change it later.
Peter

It all depends on where and how you want to drive your car. If it's to be a highway cruiser, the 3.07 is what you want. Autocross or back roads 3.9 works fine.
I like the 3.9 for the mountain roads where I live. I don't think that the 3.5L could hurt the MGB axle under normal use.
Kelly Combes

thanks to every one who helped.If i can get the 3.07 diff for a reasonable cost ,possibly Mark from Wilts, iwill fit that other than that i will fit the standard axle.How much machining work is envolved to fit the v8 gears into the rear standard housing.I am mechanicaly minded ie rebuilt the engine etc.. or does this require expert help.
Cheers everyone...anyone want a capri axle!!!!
p stanford

This thread was discussed between 07/05/2006 and 09/05/2006

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