legokcen

iTrader: (8)

I mean the Limited Slip, not the Hallucinogen Drug.

I've got a complete rear end from an 83 GSL that has been sitting in the garage for a couple of years. The donor car wasn't running when I removed it. Is there a way I can check to make sure it's still ok without taking it apart?

DAVID GRIMES

Just one way: Install it and go for a ride.

Seriously, I have the same thing rusting away in my backyard. It looks pitiful, but I may clean it up and use it one day. I won't take a chance on it being okay. I'll have to see or get someone who knows to make sure it's worth fooling with.

FWIW, my brother just removed my '81 third member to fix a leak and the ring and pinion look great. Somewhere around 150,000 miles on that rearend and never gone into before!

Dan_s_young

iTrader: (1)

You can perform a break away test. That involve jacking the rear of the vehicle up so the rear tires are in the air. Then when one person holds the one wheel in firmly in position you goto the opposite wheel and see how much rotational torque is required to turn the wheel without the other spinning.

That should give you an indication of the clutch pack condition.

blwfly

iTrader: (4)

^^ i second this what was the torque rate? 160
i may check my lsd aswell

legokcen

iTrader: (8)

Any idea how much it is? Is it the higher torque needed the better or the other way around?

blwfly

iTrader: (4)

little search and i found this by peejay took 5 seconds hahaha

Okay, here we go...

You need a torque wrench, a click type or a beam type will do, both have their drawbacks but also both have their advantages.

Jack up one (1) rear tire with a floor jack under the axle

Block the other three tires

Handbrake OFF, transmission in NEUTRAL

Can you turn the wheel easily with light finger pressure? Yes? Diff is worn, or is an open diff.

Good amount of resistance? Okay, let's quantify. The measure of a clutch type limited slip is the breakaway torque - how much force it takes to initially make the tire turn. I have never seen an actual spec for this, but 40lb-ft of torque is a nice figure. A *goood* diff will be up around 90-120lb-ft but those are a real pain to drive on the street, you're pretty much driving a spool at that point.

So how do we measure the breakaway torque? Take your click type torque wrench and set it to 20lb-ft and put it on one of the lug nuts. You kinda want to make a right angle between the torque wrench, lug nut, and axle centerline, to try and get a semi-accurate torque reading. Does the tire move before the wrench clicks? Diff's done, although it may still lock up well enough under power. Wrench click before the tire turns? Set it up higher, say to 30lb, and try again.

If you have a beam type torque wrench, you just have to watch the torque reading just before the tire starts to turn.

Either way, you have to apply a smooth even load on the torque wrench. NOTE: After the diff "breaks away" the torque to turn the tire goes down a LOT. This is normal.

Dan_s_young

iTrader: (1)

Well said.

blwfly

iTrader: (4)

thanks ill take credit for others work hahaha

legokcen

iTrader: (8)

Thanks a lot! That's exactly what I needed.

DriveFast7

iTrader: (1)

90ft/lbs is stock brand new, 125ft/lbs + for track use. My blue rx7 is set to over 175ft/lbs, i think previous owner put all oversized discs in the LSD. Tight as hell.

sctty

Does anyone have a spec for what stock is? Where does the 90 ft/lb number come from? There is a fair amount of variance in what you can get, depending on what parts you rebuild with.

85rotarypower

Well, my high mileage LSD rear end in my 82 clocked in at 80ft lb last I checked. Pretty good it seems. I would say as long as its not below 40ft lb your in good shape.

trochoid

iTrader: (6)

DriveFast7's specs came from the FSM, imagine that folks. The S3 FSM has a full chapter on diff rebuilds, I have a copy of the 70/80 diff service manual, no lsds then.