Miata LSD into 85 GSL
 

Have searched thru the tech section and achieves looking for picture of how much of the third member needs to be grinded off into order to install Miata 4.30 LSD (99 MY) into my 85 GSL axle that I am swapping into my 85 GS. Anyone have the link and or pictures; want to see the level of work needed.

Should fit right in. Have you tried and are having problems? I put a small axle RX7 LSD into the miata third member and it bolted right into the RX7 rear end.

Have not tried but in reading thru achieves and asking people; they mention that in order to use stock watts linkage system the Miata third member case need to grounded down some for clearance. Was wondering if anyone had pics of work needed.

My car has tri-link, so that might be why it fit without any modifications. It is not that hard to swap the third member, so I would just try it and see what (if anything) is in the way. If you don't get any more specific responses anyway.

Carl

I have not done the Miata 3rd member swap, but I did look into it. The Miata piece has some bulky "bosses" on the right side where it mounts to the chassis, and this is what needs to be cut/ground off to clear the watts pivot bracket. I have seen pics on this forum of the modified Miata diff but can't find them now. The mounting bolt holes need to be completely removed, as this is exactly where the watts bracket lives.

If you do it make sure you use cutting wheels made for aluminum and some "grinding grease" made for aluminum. Aluminum is a b:tch to cut / grind. I'm trying to attach pics of the Miata part showing the boss but it doesn't seem to be working.

Miata Diff showing bolt holes to be removed. My apollogies - the 3rd member is iron and not aluminum (silly me!). I had to cut and smooth some cast aluminum not long ago, and had that "fun" stuck in my head. Yeah, 4" disk grinder with metal cutting wheels, and a couple hours (maybe a dremel to make it pretty) and you're good.
https://cimg6.ibsrv.net/gimg/www.rx7...143a12e154.jpg

You want to remove this big 'ol chunk of iron, because as I said, this is where the Watts Link Pivot is mounted on the axle housing.
https://cimg0.ibsrv.net/gimg/www.rx7...64cc444c76.jpg
https://cimg9.ibsrv.net/gimg/www.rx7...39a06518fe.jpg

Sorry for the double pic post; really having issues with attachments lately.https://cimg6.ibsrv.net/gimg/www.rx7...558bf54914.jpg

Here's another pic with the FB and Miata Diffs side by side. This is from a Very informative thread on the subject over at FB.com -

Building an RX7 LSD diff - www.RX7fb.com
https://cimg8.ibsrv.net/gimg/www.rx7...c792cf4192.jpg

And here's the money shot - a modified Miata 3rd member in a FB axle housing (seen from bottom) -
https://cimg3.ibsrv.net/gimg/www.rx7...9d60f4f2ca.jpg