SD1 Half Shafts

CastleMGBV8 · Post by **CastleMGBV8** » Tue Oct 21, 2008 10:38 am

In my MGBGT V8 I have a narrowed SD1 axle, the axle and diff are fine and it has a 3.08 ratio, my main concern is the strength of the half shafts.

I have heard from other people using this axle that the half shafts are supceptable to twisting and potential breakage, whether this is a factor of them being narrowed I do not know but if I'm going to be making a few runs at the Pod it is something that concerns me, also I have never been particularly happy with the way the hubs were redrilled for the MG PCD and the way the studs are fitted, don't fancy dropping the clutch at 3500RPM and seeing a wheel diisapear up the track!

So it looks like a pair of heavy duty shafts properly drilled are required, any advice re reasonably priced suppliers would be helpful.

Kevin

bones · Post by **bones** » Sun Oct 26, 2008 12:02 pm

i looked into this before, some time back, try websters race engineering as they could get something made for you, real steel used to race a sd1 and done the strip in 11s and they had stronger shafts made and had no problems with it, loads of people told me to change the axle because the shafts are not thicker enough, all i can say to that is rubbish,

rich

ian.stewart · Post by **ian.stewart** » Sun Oct 26, 2008 1:21 pm

If my history of the axle is right, the SDi diff is interchangble with the Sherpa, now the sherpa is a good strong axle, which in turn is related to the J4 van, which, continuing the linage is the same as a Austin Westminister, this is where I am going to stop, go back 30 years and everybody who drag raced and could not get hld of an 9" used the westie,strong as fook, go back to Briscar? F1, and I think they either used either bedford truck axles or Westies. Im fairly sure the shafts are interchangable right up to the SDi axles but its worth check, there are plenty of axles that ues the same internals,
Sdi
Sherpa,
Westminister,
J4
Big Healey??
TR7/8
and a few more I cant remember, there are a few more enlightened SD1 owners who can confirm the srength of the axle and even more old racers who have abused westies

CastleMGBV8 · Post by **CastleMGBV8** » Sun Oct 26, 2008 1:46 pm

Ian,

Thanks thats an interesting bit of history.

Mine's obviously been narrowed to fit the MGB can't remember how wide the standard SD1 axle is, the B is I think 52" drum face to drum face so in the region of 8-10".

It is basically the quality of the work that was done to narrow it and redrill for the MGB PCD. I can't complain as I inherited it free of charge from a friend with a V8 MGB roadster.

I have heard of people with the same set up who have suffered shaft failures or twisting of the spline ends possibly due to the shafts not being properly heat treated after resplining.

Kevin.

ian.stewart · Post by **ian.stewart** » Sun Oct 26, 2008 2:43 pm

Shortend half shafts are allways going to be a problem, , most I would think will be induction hardened just around the splines, for any small engineering firm to be capable of doing this is unlikley, so they are probably flame hardened, this will be fairly uncontrolable and the depth of hardening could easily go full depth and up the the shaft as well, I did look into getting a pair of shafts cut and resplined by a company that does nothing else but splining and gear cutting, and they would not even entertain resplining,
BUT, I know of lot of people who run resplines without trouble, I even ran a set of welded 8" shafts without trouble,
You say 52" wide, just as a point of reference, Mk1 Capri 3 ltr is 52" wide, strong as fook with a 2.8i lsd fitted and there are plenty of upgrades available and a wide range of ratios

CastleMGBV8 · Post by **CastleMGBV8** » Sun Oct 26, 2008 3:34 pm

Ian,

I'll double check the B axle width I was going by memory and mine isn't so good these day's.

The Mk 1 3 Litre capri could be an option, I had a Mk 1. 3 litre capri back in 73 and loved it a real hooligans car and very chuckable.

Kevin.

CastleMGBV8 · Post by **CastleMGBV8** » Sun Oct 26, 2008 3:57 pm

Ian,

Just checked width the salisbury tube axle for bolt on wheels is 48.5" axle flange to flange ie inside of backing plates so my figure of 52" outer face of brakes drums is probaly close.

The capri width of 52" is that outer face of drums or flange to flange?

The more I think about it I'm tempted to slot a narrowed Jag IRS into the car using a new crossmember and dumping the jag cage.

I can buy a complete Jag rear for £250 with a choice of ratios and a posi diff.

There not cheap to rebuild though, but with a rebuilt diff exchange hubs and brake calipers and all the kit to fit it comes to about £1500 and will handle more power than I'm likely to ever put through it.

Hold on insanity's creeping in again, but it would finish the car off nicely, any idea what capri axles go for and is it the one known as an Atlas.

kevin.

bones · Post by **bones** » Sun Oct 26, 2008 9:53 pm

atlas is the one, found one on e-bay out of a 1,6 laser, £10 i think, or you could get moser shafts made for the sd1 youve got fitted £250 to £300 i would think

rich

CastleMGBV8 · Post by **CastleMGBV8** » Sun Oct 26, 2008 10:34 pm

Thanks Rich.

ian.stewart · Post by **ian.stewart** » Mon Oct 27, 2008 5:37 am

Axle from a laser would be wider than a Mk1 capri axle. I would have my suspicions that the axle is not a Atlas but a Kohln,

minorv8 · Post by **minorv8** » Tue Nov 04, 2008 6:19 am

5-speed TR7/8 rear axle is basically the same as SD1, AFAIK only narrower. So, with luck you might be able to use TR7/8 halfshafts if they are correct length.

I narrowed a TR7 axle for my Moggy and found out that I only had to shorten one halfshaft some 5 inches. (halfshafts are unequal length so swapping one halfshaft from LH side to RH side proved to be perfect solution)

Of course the flange is a nightmare since Triumph has 3,75" PCD whereas MGB has bigger PCD.

JP. · Post by **JP.** » Tue Nov 04, 2008 8:11 pm

ian.stewart wrote:Axle from a laser would be wider than a Mk1 capri axle. I would have my suspicions that the axle is not a Atlas but a Kohln,

1 = Correct
2 = Atlas is Köln axle ( English axle is also known as Tanken)

Capri axles are in three wide variations and the smallest one is from the mk1.
The early Capri mk2 axle is about 1"wider in total versus the mk1 axle.
late mk2 and Capri mk3 is 2"wider in total versus the mk1 axle.

The Escort mk1 has also a "Baby" Atlas which is even smaller than the Capri mk1 axle

The same Atlas axles but in differend dimensions are also used on Transit vans and Taunus / Cortina's.

Axles can be narrowed to almost any dimension, shafts can be bought in several lenghts and even as a full floater GP4 with seperate hubs.
Cartrac does them, Quaife does them and lots of Rally Escort builders does them.

CastleMGBV8 · Post by **CastleMGBV8** » Tue Nov 04, 2008 10:17 pm

JP,

Thanks for the information

Kevin

Ian Anderson · Post by **Ian Anderson** » Wed Nov 05, 2008 8:30 am

What tyres are you running?
If they are relatively narrow, hard road tyres they will spin and release the torque loading
Wide sticky sicks and yuor problem gets a lot bigger.

Ian

CastleMGBV8 · Post by **CastleMGBV8** » Thu Nov 06, 2008 9:27 am

Ian,

Max tyre width I can run without reducing the width of the axle is currently 195/65 x 15 Pirelli 6000, there may be scope to run a slightly narrower axle but would need to check clearance of inner tyre wall to chassis rail.

I had the inner lips of the rear wheel arches removed when the car had a bare metal respay, so no extra room available.

Ian you are right about the extra grip of using a sticky race compound increasing the torque loading on the the axle and shafts which is my main concern in view of the torque that the new 4.35 engine is going to produce.

Kevin.