what are my options ?

 

have you tried to rebuild it? Mazda still has the main wearable parts available; standard and oversized friction disc's, conical springs and thrust shims. Unfortunately the "hard" parts; the side gears, spider gears, spider gear carrier and housing are not

 

I have not tried to rebuild. My current diff clunks when I lift on/off throttle, when I jack the rear in the air I feel like I can move the wheel way to far before it contacts, not sure how to say it, maybe free play. It also spins one tire more then then other.

Any links or books that could walk me through a rebuild?
being honest I have tools and average to below average mechanic ability.

 

there should be an archived thread or 2 on it. Lemme see if I can dig'em up




*EDIT*

here ya go, overall the whole process is pretty strait forward, most of the hard part is measuring and doin math

https://www.rx7club.com/1st-gen-arch...g-soon-717591/
https://www.rx7club.com/1st-gen-arch...ur-lsd-711948/

 

a miata os giken diff will go in im pretty sure. but i think they are like $1800 bux :C

 

Check the u-joints on your driveshaft first...

I had a similar issue when I had my GSL-SE and the driveshaft was about to fall apart if I drove the car any longer than I should have with the clunking.

 

it only the 84-85 big axle rearends that have the "interchangability" w/ miata diffs (among other mazda diffs)

 

I know when I had the drive shaft made I got serviceable u joints added on both ends. How would I check the u joints and know they are bad? it does clunk, among other clunks its tough to tell what clunk is what. LOL I do have the upgraded axles if that helps figure out what 3.9 diff I have. If I recall right the miata LSD will fit inside the FB differential

 

Don't know anything about them, but I know Kaaz makes a LSD for us. I think MazdaTrix even sells them.

 

OS Giken or you=trophy bottom

:-)

 

Those archived threads are awesome, but reading them makes my head spin.

Swapping a donor or rebuilding seems the most economical route.
I'm interested in the Tosen differentials at Mazdatrix.
Torque Sensing. No clutch plates to rattle in these $1005

How do you test a LSD without tearing it down?

I have an -SE rear taken from a donor car which I have no driving history. I have it on the bench now.
If I grab one of the disks and rotate the pinion, the loose side will turn freely.
Shouldn't the side I'm holding receive the power since its the side with traction?

 

the traditional test of a LSD's condition, is to test for the torque break away, which is done while its still inside the axle housing and attached to the car. You pretty much jack up 1 side of the axle, while leaving the other side on the ground, and leave the transmission in gear. Then an adapter is attached to the hub to allow a beam style torque wrench to be positioned in the center. Apply force w. the torque wrench until the hub begins to turn and note the torque reading. I dont remember what the break away spec is for 1st gens, but I want to say that is 65-80ft-lbs.

Clutch style LSD's dont transmit the power away from the spinning wheel and to the side with traction, but rather attempts to keep both sides marginally tied together to an extent, but once it begins to slip, more power will get sent towards the easiest path i.e the spinning tire. After all, clutch style LSD's are still a traditional differential, they just have a stack of plates under a pre-loaded pressure that actively try to keep the axles at the same speed.

By the sounds of it, your LSD is tired and worn out, but the only real way to find out, is to pull it apart, inspect and measure the parts inside and compare them to the factory allowable tolerances

 

more money

 

that helps me understand the lsd, but what is causing the clunking when I lift off the throttle?

 

there are a few possibilities.

1. worn U-joints in the drive shaft

2. if you reference some of the pictures in the links ive posted. there could be excessive wear in either the "x" cross piece that the spider gears ride on or the ramps on the LSD case halves

(see post 10 by J9FD3S in the "LSD tear down link". He reference to issues that come about from excessive wear on the ramps, causing clunks on decel or throttle lift)

3. improper backlash or clearence, and/or pinion depth between the pinion and the ring gear (usually exhibits itself as a whine or growl that is speed or RPM dependant tho)

 

Love mine and it will beat the Kazz any day. I believe I paid about $1500.

 

if I was to get the os giken or kaaz LSD, I would also need to rebuild the gears and stuff too? This is one of the few parts I have not torn down and rebuilt/replaced. The whole thing is foriegn to me so anyone that has done this advice is appreciated