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MG MGB GT V8 Factory Originals Technical - Drivetrain strength - the big picture

Well we have all seen the reports that the stock B rear axle is as strong as a Ford 8". And then there is all the data on the GM and Ford T5 tranny and thier replacements. BUT there is one thing people seem to be missing that make switching to the Ford 8 or 9" a good idea, the DRIVESHAFT (PROPSHAFT). That is the weak point as I see it with using a stock MGB rear axle. The Axle flange is quite unique on the MGB, the BIGGEST Ujoint flange available to match the MGB axle flange only uses a 12-20 Ujoint as used in Ford Ranger trucks. That special flange was $80 at my local places, one place could not even get it. By comparison a stock ford Mustang Ujoint is 13-30 or bigger. I am not sure what size a MGB Ujoint is, I know it is small.

I want to bring this up so people see the whole picture. A friend of mine had a stock rear axle in his rover V8 car and he broke the rear ujoint which in turn completely destoyed the entire driveshaft within a week of getting the car on the road.

So far I have made some good 1/4mile runs with my stock axle using that 12-20 ujoint, but I have stock tires so they break loose before to much stress gets sent to the axle/driveshaft..
Larry Embrey

Larry, I couldn't agree more. The MGB uni is too puny for a V8. I got around the problem by using a modified Rover V8 driveshaft. I had the rear flange redrilled to the MGB pinnion flange bolt pattern & bolted them together.That was in 1990 & up to recently ,that car was my daily driver.Barrie E
Barrie Egerton

Larry,
An excellent point as Barrie said.
I have always worried a little about people making changes to half the car and leaving the rest stock especially things like U joints which if they fail at the front and no driveshaft loop is in place can really ruin your day.
Peter Thomas

I would be much less worried about the front Ujoint. The front yoke has to match yout tranny, unless your using a B-tranny. (Talk about a weak point!!) You will likely use a GM or Ford T5, those use a BIG Ujoint that can more than handle the stress a V8 is going to put out. BUT the REAR ujoint has to mate to the axle to if you use a MGB axle your limiting Ujoint size..

A fried can test to this, he broke a rear ujoint and it cost him the entire driveshaft..

I have been daily driving my car since it was Finished April 29th. I have somewere over 500miles on it in a month heh Taking her of road for a few days to install a air/fuel guage and go over every nut/bolt on her and checking all fluid levels again.
Larry Embrey

Larry,

Very good point.

I've knackered SD1 prop UJ's and halfshafts. In the UK all are upratable at reasonable cost.

Paul
Paul

Absolutely correct. It also gets sloppy around the flange bolts which is aggravating at best.
Jim Blackwood

Larry, the MGB rear flange can be obtain from an industrial outlet, it's the same as the early Jags. Jags use a bigger U joint, also an industrial flange with heavy duty U joint and larger dia tube. Becareful with the larger tube, room is limited.
The industrial flange is square the B flange is round these are the only differences on the mounting of the flanges.
Bill
I have used the industrial flages on all of my MG's and MK II Jag's
Bill Guzman

Bill, do you have a part number and/or Manufacturer of that flange?? The one I have uses a Ujoint out of a Ford ranger truck, it is a 12-20 ujoint, a stock Mustang ujoint is 13-30, not sure what a B one is, but I know it is like a 10 or 11....
Larry Embrey

Paul,

I'm glad I'm not the only one worried about SD1 halfshafts. I had mine cud doww and resplined when I first built the V8, after about 10000 miles they were looking a little twisted, I have been assured that it is nothing to worry about, but would like to know if I can have uprated ones made at a reasonable cost.

Mike Barnfather
Michael barnfather

Larry, I don't have the part # but you can get it from a industrial outlet. I will see if I can get it for you. It has been a long time since I had driveline problems.
Bill
Bill Guzman

Mike,

I had them made by Strange engineering in US/Canada for £400.

Andy Robinson arranged the deal as he is an Authorised Dealer for Team Strange - Basingstoke tel 01256 880589. If you can give him length of each Halfshaft I'm sure he can arrange for them to be made.

There are other ways but would cost well over £1k.

Terry Brown may have some thoughts. Do you know whether his rear brake kit is ready yet?

Paul
Paul

I have a local shop that does my work. I am just curious about the flange Bill has gotten ahold of, to see if it the the same unit I have or can use a bigger Ujoint. My place does all drivelines, cars, trucks, industrial, so I think they might have gotten me the same unit.

I have not had driveline problems YET, but if I keep going to the track I want it overbuilt, not built "just to the limit".
Larry Embrey

This thread was discussed between 19/05/2002 and 24/05/2002

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