Can someone point me to a link that walks me through swapping out rear ends (to LSD)? I searched but didnt find one.

 

didn't look for a link, but i could walk you through it. if i recall, it all comes down to the right driveshaft and matching up brake lines.

what year car? what year rear?

 

Yep, need to know the years of the rearends involved. In mid 83, the pinion flange was changed to larger one. The 84-85 rear ends had larger axles and bearings. The drum brakes have a different rear brake cable than the disc brakes. The SAs had coarse pitch threads on the brake lines, FBs have fine threads. All can be interchanged, once one knows what diffs they are dealing with.

 

If Im not mistaken they are both off 85's. I know the GS is an 85 and Im pretty sure the rear end is the same

 

K, swapping the same years makes it simpler. If you want the disc brakes you need to swap the entire rear axle unit, along with the two rear e-brake cables. If you just want the lsd diff, remove the brakes, rotors, unbolt the axle retaining plates, pull the axles out 3-4", unbolt the driveshaft from the pinion flange then unbolt and remove the differential carrier. Do the same on both axles, assemble in reverse order. DO NOT unbolt or loosen the main nut that holds the pinion flange to the diff.

If the new lsd unit comes from a GSL-SE, you swap the lsd unit or the entire rear axle and the complete front struts due to the change in the wheel bolt pattern of the SE.

The following link will lead you to the FSM, download and read/study it before starting.

http://foxed.ca/foxed/index.php?page=rx7manual

 

Anyone know what those brake line tread pitches are, specifically?

 

You also will want the softline from the body to the axle if you are swapping the disks. If its in a junkyard it wouldn't be a bad idea to grab the brake master and the proportioning valve as well. You don't need it, but it won't hurt, and mazda must have know what they were doing to make different parts for each.