Ok so here are the specifics. I recently swapped a Jspec S5 TII engine into my 1990 S5 N/A GXL rx7. I bought a turbo driveshaft and now am looking for the rear end to match it. I found a rear end for sale and here was the description:

"This is a LSD Rear Diff. From a 87 RX7 T2. These are known as some of the best rear ends mazda ever made and will interchange with several other models. This came from a car with only 88k miles so should be in very good condition."

I was told the S4 rear end is much better than the S5 and it also fits, is this true?
Also I want to make sure that what's in the picture is all i need to change on the back end...

anyone who was done this swap and changed the back end using the same rear diff your comments would be greatly appreciated.

Thanks. Here's the pic of the item for sale.

 

Yes, you can interchange S4 & S5 TII rear ends, but you will also need the TII half shafts to complete your swap.

 

The N/A half shafts dont work? bolt pattern different?

 

Also what are the downsides to fabricating a new plate with proper bolt pattern for my rear end that is in there now????

 

I don't believe it's the bolt pattern, I think it's the lengths that are different. I haven't done this conversion, so I'm going from what I recall of reading elsewhere. There's lots on drivetrain swaps, probably this is in FAQ's

 

The lengths of both the driveshafts I have now are the same when I stand them side by side. I've been trying to look for info on options but all I can find is swapping out the entire rear end.

 

The NA Diff and axles will not hold up when used with TII motor and trans..

Do it right once.

Buy a TII DiFF and 1/2 shafts and you are done

 

Ok so the 87 TII differential is not the viscous right? but it will fit my 1990 TII driveshaft, correct me if I am wrong yet. Then I need the TII half shafts for the 87 TII diff... but do I need S4 half shafts or are S5 TII half shafts interchangable???

 

With what you have pictured, all you need are TII halfshafts and you will be good to go. All TII halfshafts are the same, s4 or s5. I would price the halfshafts and your local auto parts store. The fresh remans seem to be cheaper than what most people sell the used TII half shafts for. Turn your NA shafts in to get your core back.

The tII drive shaft you have will bolt right up.

s4 TII diffs are clutch type, not viscous.

 

excellent, thanks alot guys lol this is my first project car and learning as I go much appreciated for everyones help.