I have a spare FC non-turbo open diff with 4.100 R&P. I'm planning on swapping a Miata Torsen Type-2 gear case into my FC diff. Obviously, I'll need to reuse my original 4.100 ring gear. Both the Miata and RX7 parts catalogs list two different length ring gear bolts. There are 10mm (p/n 8051-27-235) and 10.2mm (p/n 8051-27-236) long bolts listed. These same p/n's are listed for both S4 and S5, and open, NA LSD and turbo LSD. The length difference is 0.2mm or 0.008". So, there's not a significant length difference between these two bolts, but nonetheless there are two different lengths available. Both of these bolts are still available from Mazda and they cost about $5 each (10 req'd). So, I was just wondering why two different bolt lengths are listed? Any thoughts on this?

Edited comment:
Opps, sorry...I slipped-up. The size referred to is the shoulder/shank diameter, not the length.

 

lol, no idea, i would just reuse the originals, its not a torque to yeild.

i think they do ask for loctite or something

 

My bad! The p/n's refer to the shoulder/shank diameter...not the length. (https://www.atkinsrotary.com/store/7...7-235-236.html)

Correct, it's not torque to yield so I don't have replace the bolts.

The FSM calls for thread locking compound. Any recommendations on what type of Loktite?

 

i'd use the one that you can remove if you needed