85 GSL SE Differential Options
 

Hey guys,

I'm wondering if anyone has experience fixing/replacing/upgrading a broken diff for the 85 gslse model? I found one which has some kind of grinding noise coming from the diff and I'd like to keep it for the big brakes and lsd. I'm on a pretty tight budget but I thought I'd see if anyone has any nuggets of wisdom!

Roland

Sorry, only $$$ and wrench time is going to get a rearend back in shape.....I went cheap on my help but spent coin on parts...Moser axles, OS Giken 1.5 diff, new bearings and seal are a must.

Wow yeah that is hardcore. I've been doing research into new ring/pinion, and i keep seeing 94-01 miatas mentioned. Have you heard of anyone just swapping in the gears from a miata (might be cheaper if i can find something at a wreckers)? I just want to get the car on the road.

Roland

You probably want to pull the axles and gears to see what you are working with first. Could even just be axle bearings?

Check bearings first, but 1.8 miata stuff will fit

Subbing. Just want to see what you do hear... my GSL-SE diff has made weird noises for years now, never figured it out.
https://www.rx7club.com/1st-generati...r-end-1077112/

These diffs can be fully repaired - parts are available from Mazda, Atkins, Mazdatrix, etc. This includes bearings, seals, crush sleeves and clutch pack parts. In my experience ring and pinion failures are rare. Axle bearings and bearings in the differential are more likely to fail.

There is no real magic with respect to a GSL/SE differential. Limited slip differentials from 84-85 GSLs are the same thing. Also, limited slip differentials from earlier FBs can also be used if the side gears are changed to allow for the larger 84/85 axles. The diff in my race car was in an 82 GSL and when I switched to the larger axles I had the side gears changed out to make it work. Oh and the factory clutch pack diff works very well for racing....

Ring an Pinions can be sourced from 1.8 Miatas (4.77 gears are real cheap on ebay) and Kia Sportage 4x4 front diffs.

I am currently preparing my large axle housing for a rebuild. I will be running it with GSL axles/calipers.

I have sourced everything for replacement with the exception of the diff unit itself. My housing came with ring/pinion but no diff. Everything is available from the dealer or Rockauto. I went with OEM axle retainers and seals, and can get good quality SKF bearings for Rockauto.

-Find a stock one and rebuild it
-Find a 1.8L Miata unit (Most likely cheapest, can find a Miata Torsen third member easy)

I am going to go with either KAAZ 1.5 way or Tomei 1.5 way replacement diff. About $900. Slammed GSL has the ultimate setup, a OS Giken is the best you can buy.

Not many FB guys seem to be running a KAAZ or Tomei as a replacement, but these diffs overall get good reviews.