Bad engineering practice to change the stud pattern on axles by redrilling.

Utility8

Not sure. If you talk to a good diff specialist, they should be able to point you in the right direction regarding compatability. I have only had experience with replacing early banjo with complete 9" assemblies.

Utility8

Hi Phill, the original studs are drilled & pressed into the flange in virgin steel. The studs endure loads including sheer & torsional. The flange needs to be strong enough to keep the studs stable. From factory, this is achieved, and the load is managed by the integrity of the the flange as a whole.
As a new position for the new holes is required, I make the assumption that the access holes between the studs in the factory flange will need to be plugged, drilled & new studs fitted. To do this, the integrity of the flange is then compromised. The sheer & torsional loads are then relying on the quality of the weld. X-ray is probably the only way to confirm correct weld penetration. The heat required to plug the factory holes for the new stud position can have a detrimental effect on the metals structure. The axle can be more susceptible to fatigue & this can induce failure. This leads to a car going slower down the road than the rear wheel when it pulls the studs out of the flange or breaks clean off at the bearing. Even though the stud pattern in question is being reduced, HQ to Early Holden, the problem still exists. Billet axles, although a little dear, are the safest way to achieve a different from factory setup.

Multi fit wheels are a different kettle of fish. They experience different loads compared to the axle flange. The wheel nut exerts compression on the wheel hub. The material that is between the required hole & unused hole next to it is sufficient to cope with this type of load.
Vintageholden, consult an engineer that can sign off on modifications to vehicles in your state. Ask him the same question. Be guided by him, seek a second opinion to clarify. (dont believe the diff builder unless he can supply the correct engineering cert for you to get it through rego. None will.)
Happy Days.


Utility8

Edited by user Tuesday, 8 September 2009 7:43:02 PM(UTC)  | Reason: Not specified

I suppose you could have an axle with multifit stud holes, but axles usually have extra large access holes to get to the retaining plate bolts. This makes the ability for there to be more than the one set of stud holes unpossible. As for welding and redrilling holes, that is not a good idea. Especially when using press fit studs. The studs are retained by the interference fit in the hole, utilising the consistent metal available when it is a virgin hole. If you weld and redrill, then you have inconsistent metal, and therefore the known quantity of a press fit stud in a consistent metal is no longer available. How could an engineer sign a report with an unknown quantity?

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