I am currently seriously considering to buy an 1989 RX7 GTU on tight budget. However, I found out that the FC in this trim for the S5 does not come with LSD. Which LSD would fit the 89 GTU? What components would I have to change in the currently stock rear end? How much would all this roughly cost? This would be my first Rx7 so I would probably need to go to a tuning shop to get this job done as well. Also planning on tracking the car a lot

 

miata torsen differential or t2 lsd would both work with modifications

an s4 or s5 na lsd would work with no mods

 

Would the FC3S S5 KAAZ LSD 1.5 fit on it? What additional modifications would I need to make for it to work? Also what is the average price for labor if I were to get a car shop to install it? I don't really have a good concept of how everything works so I don't want to mess it up by myself

 

Hey Henry,

If you are using the same housing and axels, there are no real modifications except actually unbolting the ring gear from the diff. The Kaaz 1.5 is very nice but it is an expensive piece. The critical part of the project (assuming you can drop the subframe and take the differential out) is making sure you set the lash when you put the ring gear and actual Kaaz/Torsen/Guru/OS Giken back in. There are lots of 4.1-1 gear ratio limited slips out there, my guess is you can get one for a hundred dollars or less. Change the fluid and go.

I would check your ratio, you may have one of the rare ones like a 5.12-1 or 4.88-1. I just sold a 5.12 for $1600 and a 4.88 for $1100. IF you had one of those,somebody would trade you a rebuilt one and give you cash on top of it too.

Good luck

Steve