87 xj6 s3 rear end high hop question

I’m doing a 2jz engine swap on my 87 jag with a stock 2j auto trans (will end up building it for more power) anyone here that’s done a high go jag? (700hp+) ls or what ever engine swap. Wondering what to do for the rear end to handle the power etc. thanks for information in advance

I’ll mention a couple of things that I would have a concern with. Add another set of radius rods from the bottom of the IRS cage to the body near the “frame”. Gusset the body and maybe use Hiem joints on either end. Make an attachment point at lower tie-plate of cage. This will keep the cage from trying to rotate up with the differential.

Hub carriers have been know to develop cracks where the lower wishbone connects. If you study the geometry and where the forces are applied, you see that the forward force of the axle, against the resistance of traction, makes the hub carrier want to revolve around the main radius arm. The only thing preventing this from happening is the lower connection of the hub carrier to the lower wishbone. Terrible amount of torque strain in my opinion. I have read that about 350hp is the comfortable max for a stock IRS. In a lighter car like a kit Cobra, this is not so much a concern because wheel spin can be achieved quite easily, reducing the strain.

All this being said, there are lots of LS swaps into these XJ cars and they must hold up to some degree. Study the weak points and let your experience be your guide.


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I think Dave’s suggestions/thoughts are good.

Beyond the IRS I wonder about the differential coping with 700hp

I also wonder about the the structure of the car coping with 700hp


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Me too… that is WAY beyond the original engineering envelope.

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“Keep the tires loose,” and it will live. I have a '77 XJ12L with a 3.54 posi hooked up to a Big Block Chevy. Only 485 HP at the crank. It has been to the drags with street slicks, Mid Ohio Sports Car Course for HPDE, and flogged on the street. Different rear than yours, but similar.