A-Series diff w/ wrong flange PCD - Swap tail-shaft or flange?

[AndyTTR]

Hi all,

I've searched the forum and found a stack of info on this problem already, just after opinions on the best course of action in this particular scenario.

A friend of mine asked for help fitting a complete A-Series LSD from a JZA80 Supra to his UZZ31 Soarer.

I've fitted the diff up fine, but when it came to bolting up the tail-shaft it turns out that the diff is from an Auto JZA80 TT and not a Manual NA (which has the correct PCD for the Soarer) like he was told.

The problem here is that the PCD of the input flange on the diff is bigger than that of the doughnut and existing Soarer tail-shaft.

So there are two options I've trawled from the internet:

1. Find a JZA80 TT Auto tail-shaft and make a hybrid with the existing UZZ31 shaft.

• Pro: Doesn't involve messing with the diff. Centre bearings are the same between the two models, should be an easy swap.
• Con: Don't know if the length of the rear section of a Supra tail-shaft is suitable for the Soarer. Also have to buy a tail-shaft.

2. Swap the flange on the LSD diff with the one from the original open diff (un-bolt and bolt-on without opening the cases).

• Pro: Cheapest and easiest option (if it works the way internet people claim it does).
• Con: Not sure if it's safe to simply swap them over. The method for swapping the flange in the TRSM is ~10 pages long and involves complete disassembly of the diff... not as simple as just swapping the flanges.

Does anybody have any tips / advice on how to go about this? Any help would be greatly appreciated!

Cheers,
Andy

[lt1972]

Can you get an offset adapter plate to go in between the 2 flanges?

[madmont]

you will need a deep socket to take off the nut holding on the flange

[AndyTTR]

lt - would prefer not to use an adaptor... hoping there's some combo of factory parts which can make it work.

Madmont - yep, 36mm deep socket. Already got one.

Is there anyone on here that has swapped the input / companion flange on an a-series diff before?

[Cuzzo]

The nut for the flange..is that the pinion nut?

[AndyTTR]

Yeah... I think it is which makes me reluctant to just undo it and swap the flanges...

It's the nut in the yellow square in this picture. The flange we want to swap is in the blue square.


It seems pretty common on US / UK forums for them to do it... it just doesn't seem right to me. lol

If the bearings are pressed onto the pinion shaft then undoing the nut should be ok yeah... because the shaft won't move longitudinally (in/out of the diff) without being pressed? As long as I torque the bolt back up properly would everything be ok?

[love ke70]

dont take this as gospel, but in theory, if you mark the nut where it was before you undo it, and do it back up to the same spot, everything should be ok...
or better yet, mark the nut, back it off, then tighten it to the mark, and determine how much torque you used to get it there, to allow for difference in thickness in flanges retighten to this same torque with the new flange and all should be well,

that is assuming the flange comes out the way diagram depicts