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I just inspected my differential and I can say I've never seen such a clutch type LSD like mine before. The clutch package isn't preloaded at all. All the LSD diffs I know are preloaded in one way or another. Did Mazda really build differentials without conical springs for the first RX7s or am I simply missing them because of a stupid mechanic?
In a detroit locker style LSD, common on American cars, You have the spider gears in the center then two springs, one on either side, then the clutch plates after the springs. The springs put load on the clutch plates giving you your limited slip effect. The heavier the springs, the more preload applied to the clutches.
In an rx-7 differential (not sure what the name is for the type?) you have no springs acting against the clutch packs on either side. So how is the limited slip effect created? If you look at the two end pieces to either side of the spider gears in the center you will see the inside surfaces are angled or ramped. When torque is applied to the diff the center spider gears push apart and push against the ramped sides, causing the end pieces to push outward against the clutches, thus creating the limited slip effect. The angle of the ramps determines how quickly, and at what torque the LSD engages at.
I am sure my technical lingo is not totally correct but hopefully this makes some sense.
Oh also, per j_tso's post above, there are conical washers on either end of the clutch packs... They are BARELY conical so if you aren't paying attention you might just assume they are flat washers.
Detroit Lockers are not limited slip differentials. They aren't even differentials. They are more like ratchets that allow one wheel to overrun the carrier.
I have one in the RX-7 now and it's pretty neat to drive. When turning around corners it sounds like you're going up a roller coaster start hill. It's a little odd feeling during the moment when getting on the power exiting a corner and all the power goes to the inside wheel until it starts slipping enough that the ouside wheel engages. Before that it feels like an open diff, after that it feels like a spool, and in the transition there's a little side jerk. Since tires get traction by slipping slightly, the inside tire slipping is "normal", but it is definitely weird feeling to first be thrusted to the ouside of the corner then thrusted to the inside.
Ok, I figured I had some things wrong there. Regardless though, my description of the rx7 diff still stands to explain why when you rebuild it the stacks will always be loose.
RX-7 diffs are standard "Salisbury" type diffs with the wedge ramps and such.
(Some) American rearends have some real bastard POS junk that uses the side gears as the wedge ramps because they had to accomodate C clip axles. So the only kind of preload spring available is an S spring that you shove in between the side gears. One of the hallmarks of this design is that as the friction material wears, the gear clearance goes up and the axle end play goes up. I've seen 1/4" (that is .250" or 6.xx mm) of end play on a work out Traction-Lok before. Shameful!
Here's me driving my Locker equipped car. In tight turns you can hear it ratcheting. Really cool.
04-20-18, 01:35 PM
