When the diff shop shortens an axle, how do they do it, or is there many ways it can be done?

Cut splines off and re-spline?
Cut at other end of axle and re-join?

Cheers

p.s. Im not going to try, just want to know

There are two ways of doing it. Where the axle is thinner than the OD of the spline further in where it needs to be once shortened, the axle is cut down, and ends vee'd out, and welded back together. Then the welds are ground back, and the axle is straightened. I'm fairly sure that the axle is heat treated before and after welding also.

OR, the axle is cut down, and resplined, then the new end is re-case hardened.
People who like the cut and weld method don't like the cut and respline method, because they say there is a plane of weakness induced into the axle where the new spline stops. And guys who are a fan of cutting and resplining, don't like the idea of welding something which is of such a high tensile nature. I supose both methods will work providing they are done right. (I prefer the cut and resploine method.)
On many datsun axles I've inspected, the OD of the splines is larger than the OD of the axle itself. I think this is because the splines were hobbed onto the axle when they were manufactured.

BOth options have pluses and minuses. One of the only times i've personally heard of a cut and welded axle, it was on a front wheel drive, and was to adapt the driveshafts - welding hte inner half to suit the engine transplant, and the outer half of the axle was the driveshaft for the car the engine/box was going in (specifically it was a rover v8 in a mini).

There are those who think that the shorten then respline is a good option - if it is hardened a fraction less (and i don't understand metallurgy enough to know exactly what they do to them to achieve this) than the original, and then racers inspect the axles every few drag race meets and when the splines start to show signs of twisting, they replace the axles..

This will probably _never_ happen on a datto (thank god) but there was one or two diff places in melbourne who worked out that 28 spline bw 78 diff axles were 'compatible' with the 28 spline ford 9" diff. So they used two axles from one side (the long ones - so one was going in 'back to front, and had a lifetime of stress/force in one direction, and was put in the other side) from a certain commodore, and it would be just the right total width for a hq or something like that. That brought up many problems - the aforementioned axle in 'reverse' as far as it's stress history went, second, with equal length axles, the diff pinion was no longer centred in the car - cocked off to one side a little - even if it cleared the trans tunnel, hardly 'brilliant' - and third (perhaps worst of all) the commodore stud pattern is metric HQ is imperial. They will physically fit, but there's a 0.6mm difference in stud spacing - it'll bolt up but be under significant stress, and likely to fatigue crack the studs eventually....

Reason I mention this is that this isn't a job to be taken lightly, and there's some snakes out there in the industry. It's one of those things worth paying a little bit more for and trusting to a firm with a good name/track record.

with an angel grinder

jarrad
go and see phil purser at final drive
tell him darren fromm southsides sent you
he does good work
he resplines which i was worried about, but he has never had one fail
hes going to do my hilux diff for me when i decide on a wheel offset
dazza
ps: have you looked for that pipework?

My dad's done about a dozen Borgwarner BW78 into 1600-wagon and 1200s over the years. He cuts the axle and resplines just the one. So long as the resplining gets 're heat treated' there is little chance of failure that wouldn't have happened anyway if you are running huge power and sticky slicks.

Cheers for the info guys.

Dazza Im going to ring final drive tomorrow. I want to shorten the axle at the flange end. The local diff guru said it could be done, but will look into it in more detail.

Sorry Dazza, had another look and asked Dad. Old CA bits are gone.

phil will tell you the same as me
DONT

why would you want to shorten it at the axle flange anyway?

coz really if theres one place you dont want a weak spot its on at the outside end of the axle...cant say loosing a wheel would be all that fun

whereas if it breaks at the centre it just makes some bad noises and a mess of the inside of the diff

Spoke to Phil

He's got some blank axles, that he can spline at the correct length and then drill and put the desired studs in. Going this route rather than modify old axles to do what I want.