Allright, I give up. I remember a thread that answered this question, but I can't seem to find it. I'm looking for an LSD 3rd member for my Rx2. I found an 82 Rx7 that has drums but, the diff feels as tough it could be a limited slip. Then agan it could be that the diff is gummed up or something. Its hard to tell because the brakes are also fairly locked up. Any how... this particular diff has a threaded pinion flange. Is it a limited slip?

 

Alright, the ONLY LSD that Mazda made in the states that will fit is the early 83 RX-7 GLS diff. This was the only threaded-flange unit with an LSD. In mid 83, they went to thru-holes on the flange and went to bigger splines, which is why those diffs won't work (at least not without a lot of JB weld or something)

I don't know how to look at the diff and know, but there's a chance that it is an LSD. With the rear end on jackstands and the car in gear, you should be able to turn a wheel slowly and watch the other go the other way. When in neutral, you should be able to quickly spin the wheel, feel the diff catch, and watch the other side turn the same direction.

You'll only find these diffs on 83 RX-7s with rear discs and threaded holes in the pinion input flange, so be checkin the junkyards, yo.

 

i am curious to see why you say the LSD rearends from 81 and 82s don't work, i know that they are internally the same as an 83 rearend. Also as i recall from friends that have raced the 2's with LSDs you will still need to remove about 1/8" from the end of the axle.

 

I might be wrong, but I don't think that the 81-82 GSL had an LSD. I think they got rear discs in 81, and added the LSD in 83, which is why I said early 83. Let me know if that's not the case. My axles slipped into my stock housing and 83 diff without modification.

 

I have a complete '82 GSL (10/81 build date) axle which has discs and limited slip. IIRC, that one has a threaded pinion flange. From personal experience, I can tell you that the pinion flanges will interchange; I used my '79 pinion flange on an '83 limited slip by removing the oil slinger/shield from the early flange (wanted to keep the replaceable joint driveshaft). AFAIK, Mazda didn't offer the 1st gen with LSD and drums, but it's entirely possible to use a LSD in a drum axle, as long as the axle splines are the same. So, you may have a crossbreed axle of some sort there.

I also found some offbeat 2nd gen interchangeability; I used a 1st gen driveshaft for the Abomination (rotary Spitfire). I used a 2nd gen diff, and the locating ring on the driveshaft is a perfect match for the recess on the pinion flange. I redrilled and tapped the pinion flange for the 1st gen bolt circle.

 

according to all the known literature i have seen and read Mazda didn't do a LSD with drum however i have seen several done after the fact, ALL GSLs (GSL or GSL-SE) came with LSD units (speaking first gen only) i understand completely wanting to keep the replaceable ujoints that's why i have purchased several of the NEW driveshafts from Mazdatrix they are made with new components for all years with replaceable ujoints not staked and they cost a little less than an new one from Mazda. I could not remember which flanges were which i was thinking that the 83 rear end had the same flange as the 84-5 which is not threaded....

 

Sweet, thanks guys the car is was looking at was kind of a rare bird. It had drums and an LSD. But the yard wanted too much for it. Nomatter though. One of the guys on the forum is shipping me one.