im working on a v8 swap, and i wanted to know a couple things.how strong is the rearend if I change the stock diff for a kaaz lsd and maybe some upgraded axle shafts?

 

Friend of mine has a LS2 in his RX7, stock diff. (Launched and the ring/pinion exploded and burst through the differential case.)
I'd say at about 400ft/lbs of torque, depending on the tolerance or backlash in the ring and pinion... (case to case based on wear), you might start shearing at this level.

Your weakness in this case will be from sudden acceleration, most likely from a stop.

Do not take my words as ultimate fact, I have no data to prove this.
This is simply from one account of what happened.

 

so will a aftermarket ring and pinion gear fix that

 

That's a good question.

I don't know if the failure point was at the teeth engagement, or if it just propagated from there.
Perhaps the overall thickness and build size and material selection is the weakness.

Next would be the axles.

What I plan on doing, is swapping over the cobra rear differential and diff cradle sub assembly into my 2JZ rx7. But that's a long way down the line.

 

yea i dont think i have that kinda money just laying around for a cobra rear end

 

What about a supra rear?

 

sold my 87 rx7 with a 330 h.p. small block chevy and a m-21 muncie 4 speed to my brother (na car not a turbo 2) i never had a problem but the first time he took it to cordova drag way he broke the drivers axle -the car im building now is a 87 turbo 2 the ring and pinion and axles are bigger in the turbo 2 cars 8 inch ring gear vs. 7 inch in the non turbo cars also i belive the axles are bigger in diameter --still not good enough but im going to try it the 87 im building now is getting a 462 big block chevy with 500+ footpounds of torque at 5500 rpm . grannys has a kit to put a 8.8 rear like whats in a mustang or explorer for around $1000.00. bolt in rear from them will cost over $3000.00.i hear a thunderbird super coupe rear works and its independent. hope some of this helps.