Dudemaaanownsanrx7

iTrader: (23)

My torsion differential broke the in my 3rd gen so i bought a used s4 TII clutch style differential to swap in place. Here's the thread in the 3rd gen section https://www.rx7club.com/3rd-generation-specific-1993-2002-16/differential-took-crap-need-advice-820994/

Anyway, I figured I could get more advice posting in this section. I would like to know if there is a way to test the differential's lockup abilities outside of the car to get an idea of it's condition. Also I read a couple tricks to freshening up a clutch style differential in the first gen section was to either machine about 1mm off one of the cone surfaces so that it was able to clamp down tighter on the disks, or another way was to use thicker disks. Due to costs I would rather not rebuild the whole differential if at all possible, but i would also like to insure everything works well the first time I install it. Does anyone have advise on these cost effective methods or other alternatives?

Do these clutch style differentials usually require rebuilding? Or do they generally hold up for a very long time? Is it hard to take it apart to measure and inspect the disks and replace the most warn parts? Any special tools required besides calipers? Thanks for any advise you guys can give me, and that's all the questions I have but if there is more helpful information i should be aware of please let me know.. Thanks

-Brent V

pistones

iTrader: (5)

well unless you are sure of the mileage and the abuse that diff has seen, you should probably rebuild it while its out. my original diff had about 140k miles on it and didn't lock up for ****. The clutch types DO require rebuilding, depending on mileage, fluid maintenance, type of driving.
It isn't that hard to take the diff apart and inspect for wear( unless you don't have the proper tools or equipment.) If you only have a tiny set of tools, your best bet is to bring the diff to a professional rear end specialist. that way you don't need to buy the special tools and you won't have to worry about it not being done right.
If you have never installed a differential ( assembled the carrier into the housing and set clearances), don't do it. i did mine myself and ended up doing it twice. not fun.

Dudemaaanownsanrx7

iTrader: (23)

I have a lot of tools and a full shop so that won't be an issue. I decided i will take it apart and inspect all the parts and replace the ones that are worn, as well as either machine a little off the cone surface or shim it to get a bit more lock and maybe more mileage out of it. I was reading quite a bit on an mx5 forum and they have some good information about the s4 tii differentials as its a popular choice for the auto x cars. I have never messed with differentials before but i've done pretty much everything else and feel confident i can handle setting the backlash and bearing preload. Why did you have to do your twice? Did you not make any adjustments the first time? Did it whine or clunk after assembly? Thanks for the information!

NotTTT

Setting the backlash and the pre-load is pretty easy with the proper tools although VERY time consuming. I've done a few. Not my favorite thing to do by any stretch of the imagination, but doable for sure.

As for the diff itself. I would NOT NOT NOT shim it unless you're only into drag racing. I did that when I rebuilt the S4 diff that I swapped in when I was N/A and it was the WORST thing that I did for the cars handeling. Honestly, I should've left it as an open diff. The lock-up was WAY to much and forced the car to understeer under acceleration. If I got on the gas to early coming out of a turn, big time understeer. If the revs were high enough that by lifting the nose would be pulled down, the tires would catch and the car would turn. Often times though I found myself correcting, stabbing the brakes to get the tires to bite, turning again before getting back on the gas. Certainly not the fastest way around a track. But if all your doing is drag racing, by all means, shim it. However, if you plan on some auto-crossing or spirited street driven, I would rebuild it with stock pieces if the discs are worn.

FWIW I bought an S4 TII complete rear-end, took the S4 TII clutch type diff out, wrapped it up, stored it, and dropped a Torsen in

Dudemaaanownsanrx7

iTrader: (23)

How tight did you shim the clutches? I heard a little bit can make a huge difference in the lockup force and if you give it too much it's basically like a permanently locked differential.

The backlash seems very straight forward, the FD uses shims instead of the rotating adjusters like the TII differential. I still am not sure which method I'll have to use, but I think it's the shim method. There is no information in the FD FSM about the carrier bearing preload. From what i gather in the S4 manual the same adjusters for the backlash set the carrier bearing preload. Since the FD doesn't have these adjusters would it just be a matter of torquing the bearing caps down to set the preload?

NotTTT

I used the Mazdaspeed pieces available through Mazdatrix. I wouldn't rec doing it unless you're only into drag or have huge sticky tires out back. It MAY work OK then but it was a complete dissaster on my FC.