What brand / Weight do most people recommend for this Car and what is the best additive to use. (LSD equipped)

 

this is what i said to them:

Differential Size/Type : Limited Slip 3.9:1 gear ratio
>Transmission Type: 5-speed manual
>Issues : I am trying to smooth out synchronizer functionability and
>reduce gear grind in my transmission. Also, I want to put the best
>oil i can buy in my differential.
>Recommendations : Can I use your 75-90 gear oil in both my
>transmission and my limited-slip differential (L.S.D.)?
>Mazda calls for 75-90 in both, but I read that the your synthetic
>75-90 gear oil is for use in racing L.S.D., and not sure if i can
>use in a non-racing application.

Zach,


this is what red line sent to me:

Zach,

Thank you for contacting Red Line Oil, in your RX-7 transmission I
would recommend the MT-90 in the transmission and the 75W90 in the
differential.The 75W90 contains a friction modifier so could be too
slippery for the synchros in the transmission, Mazda calls for either
a GL-4 or GL-5 75W90 in the transmission and a GL-5 in the
differential. The 75W90 can be used in a racing differential but a
dedicated track car would generally use one of our other gear oils.

Regards, Dave
Red Line Oil

 

I use and recommend Redline "75W90" for the rear diff.
The LSD additive is already added into the fluid.


-Ted

 

Do you need Differential Fluid if you do not have a Limited Slip Differential system?

 

No, but some have claimed that gear fluid with LSD additives quiets down a non-LSD rear end.
It doesn't hurt anything.


-Ted

 

I got Royal Purple Max Gear, and it has additives in it.