I've been contemplating upgrading the stock diff for a better unit. Partially because of the clunking i get from it on accel / decel transitions. There is quite a bit of play loading / unloading the input flange (and it's already a lower millage JDM 4.3)

I drive the car very often, sometimes daily all week, including in wet weather. I also will be taking it to the track occationally on street tires. Is a 1.5 way a bad idea for this?

What diff would be best? I'm also interested in a slightly shorter gear ratio. The gears are a bit long with my tr6060 six speed even with the 4.3

 

1.5 way is the correct part, I would not want a 2 way for street driving.

The ATS carbon is the best LSD unit I have found. No chatter in slow speed cornering like some other aftermarket units. ATS LSD (93+ RX-7)

If you are sticking with the FD diff you have 3.90, 4.10 & 4.30 from OEM, then Mazdatrix offers 4.44 & 4.77

 

Rx-8 ring and pinions are interchangable with the FD. 2004-2008 manual RX-8's have the 4.44 R&P. You can find RX-8 diffs for cheap.