Hi Guys,

I am trying to help my friend out who has put a RX7 8" gear LSD into his Miata. The diff was build up by a local shop and when he installed it the axel splines going into the diff were a loose fit causing the diff fluid to leak out past the seals. I figured the shop must have built up the diff using a 1st Gen LSD unit that does not use the same type axels as the 1.8L miatas and 2nd Gen RX7s.

He went back and the shop said they did some work on it but it is not clear if they changed the actual LSD unit from the 1st Gen to 2nd Gen. Since the unit is now in his Miata pumkin / pinion nose I can't tell him from looking at the pictures what Gen the LSD is from.

I'm hoping that someone more knowlable than I can spot a 1st vs. 2nd Gen diff just by the internal unit. The casting has the number LOM32 on it

 

More pictures

 

I can't tell you for sure what it is, but I dug up some info in the 1st gen section that may help you out.

This thread too: https://www.rx7club.com/1st-generation-specific-1979-1985-18/small-axle-1st-gen-lsd-carriers-559439/

And the other thing is that I'm 90% certain 1st gen's had 7" rear ends like the 2nd gen non-turbos. The only 8" rear I know of is from the TurboII, which were all LSD as well. Hope that helps.

 

Sorry, my mistake... yes it is a 7" ring for both the 2nd Gen RX7 and 1.8L Miatas

 

First gen RX-7's (79-85) have a live axle. The second gen's (86-91) have an independent rear suspension. It should be pretty obvious if you still have the entire differential.

 

if it's leaking fluid it probably just has bad axle seals.

as long as there is no play in the axle back and forth your axles should be fine.

again, first gens had live rear axles, so you probably have an second gen diff...

 

Don't have the orginal RX-7 assembly so that is why I'm having trouble IDing the internal unit.

 

The Diff was rebuilt with new seals but there was play up and down and in and out. My friend brought it back and left it with the shop to fix it. The explination as to how he fixed it was less than clear so my friend wanted to know if the shop has now put int he correct LSD unit (2nd gen).

Is there any visual differeance between the LSD unit (the parts inside the housing) that would alow us to identify 1st gen and 2nd gen LSDs?