Welcome to our Site for MG, Triumph and Austin-Healey Car Information.


MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGB GT V8 Factory Originals Technical - MGB V8 - Axle conversion

What are my options for changing the rear end ratio on my 1969 MGB conversion? Any ideas? I would much appreciate your help...

I've got a converted SD1 axle and 14" wheels. I've tried 3.08, and 2.84 ratios. I think the 3.08 is a little low, the 2.84 gave me over 30 mpg at motorway speeds, but was a little high around town, so Im going back to the 3.08 with 15" wheels and 65 series tyres, which hopefully will be about midway. If your diff is sound, you might consider bigger wheels and larger diameter tyres.

Mike Barnfather

Michael barnfather

Thanks Mike,

I have 15" wheels but my diff is too low. I need like you said 3.07 or lower. New motor with tons of torque but no first gear to use. Do you know what happened to those aftermarket crown-&-pinion inserts that were made a while back for easy replacement? Any other ideas as for sources etc. in US or more so in Canada?

Please let me know :)

I think Mike Satur sells those gears. It might be easier to just get an MGC 3.07 rear end; I realize they aren't that cheap at around $500. What tranny do you run, and what size tires?

It is worth noting that not all MGCs had the same need to be careful. Crown wheel & pinion sets are available...try Clive Wheatley. The following site may be of interest as it lists a US distributor. Pete
Pete Green

You're right about the MGC ratios. I'm pretty sure that the non overdrive version came out with the 3.07 and the overdrive version had 3.3:1

Bart, I think that buying the crown wheel and pinion and having the carrier machined in order to fit the gears is going to cost you at least around the 1000 canadian dollar mark. I have been looking around for a while for the best option and think that now that I'm back in Australia that the easiest way to go will be to get a Ford or GM axle shortened. You also get a big choice of ratios and the option for lsd. HTH

david staines

I am on a short visit to Australia but will be back in USA by the 15th Sept. The cars here are a joy to see and hear !
I have a 78 MGB that has been converted to a 3.5 Rover and overall am pleased but it has not been with out problems. Let me list them: A Transmission went out. This was from bearing failures. This had Automatic transmission fluid installed. I purched one from the individual that converted the car. ($400-$500) This time I put 90WT gear oil.
B Replacement trany has syn. out in 2nd gear but I shift it like a old lady !
C Engine uses twoquarts every 3000 Miles. It has done this since rebuild.
D Gears that were installed are extremely loud. I would go with T5 tranny if I would have known all this. Also I would not recomend person doing work do to warranty issues. If more info is needed pls E mail and I will give more information. Leroy
Leroy Cook

You could also do the "std" V8 axle conversion and install a narrowed Ford 8" axle. (actually 8.8") Then you will have loads of gearing options, and I believe they can be changed on the car.
Larry Embrey

Aussie guys, can you recommend a good Aussie GM or Ford rear end to convert for use in an MGB V8?
mark mathiesen

Mark, Stainzy,
Ford 9" diffs are chopped to fit in Cortinas & Toranas so why not MG? Might be a bit heavy though. Valiant diffs use the same spline pattern as MG. That might be the way to go, keeping your existing half shafts.I used a Ford 8" out of a Falcon (3.08), it also has the same spline pattern as MG, but I don't recommend this route as the pinnion is about 50mm off centre if you keep your existing halfshafts.To centre the pinnion requires new halfshafts to be made ,which means very very big bickies,unless you know a friendly machinist.I never followed up the Valiant option , but I think it's worth investigating.HTHs
Barrie E
Barrie Egerton

What in heaven's name does "HTH" mean?

Hope This Helps
Barrie Egerton


If I was looking for a new rear end, I would consider the Ford Cossie IRS set up depending on availability of Cossie parts.


Paul, by Cossie I presume you mean Cosworth?. Unfortunately in Australia the Cosworth and Sierra parts are really expensive. For example a 5 speed Sierra box with no warrantee and no return is about $500 Aust. I would imagine the cost of a Cosworth rear end would be in excess of $2000. On the other hand, Ford and GM parts are everywhere as are 4.4 litre P76 versions of the Rover V8. I bought 2 P76 V8s from the parts yards for $50 each! Hence my interest in Aussie muscle car rear ends.
mark mathiesen

I understand from previous threads that a Volvo R/E can be shortened to fit, is very strong and has massive rear disks.
Angus Davies

Angis, I've heard this in the past as well.
Is there a certain model Volvo that is used. If so, do you know the ratio of that rear end?

I have a '71 V8 converted roadster that I am very happy with. It has a Ford 8" rear axle. I have not had the car for long so I cannot comment on its durability as I haven't given it a really hard time. I am re-thinking the whole rear end set up and am looking at IRS options or just improving what is already there in terms of weight, stability and geometry. I am interested to know more about the Volvo setup mentioned or even Jaguar setups other than the one on the web site. I am looking for a more street performance setup than a race one. As far my existing set up goes has any one had experience with composite rear springs, anti tramp and panhard rods?

Regards Graeme
Graeme Weston

For anyone who is interested I have gathered a little info over the last couple of years of the BBS and by going to salvage yards. The Volvo rear end is available in several different ratios but the highest is 3.3:1 so you won't be able to get a 3.08:1 or the like. The thickness of the axle tube is the same as the MGB so will accept all the same brackets etc.

The model you should go for is the 200 series. ie. 240 244 245 etc. The axle needs to be shortened by three or so inches and the bolt pattern has to be changed as well. They do have disc brakes though so this is a bit of a bonus. Several models in the 200 series have lsd but I can't remember which ones...I think the GLT has one.

A bit of info is available from Volvo websites as well.

Graeme, I bought some anti-tramp rods today and they seem to be very good quality but I haven't fitted them yet. They were $240 from the House of MG in Brisbane.


david staines

This thread was discussed between 16/08/2001 and 31/08/2001

MG MGB GT V8 Factory Originals Technical index

This thread is from the archives. Join the live MG MGB GT V8 Factory Originals Technical BBS now