Geoffrey

The locking ratios don't have anything to do with percentage of lockup because that is a function of a) The initial breakaway torque and b) the ramp angle. The numbers are simply a way to describe the characteristics of the lockup.

nathanUK '81 930 G50

Ken, my question was at what tq will the LSD start to slip? I think this is called preload.
I wondered if you discussed this.

Thanks guys.

kens911

no I didnt discuss that with him other than the fact that he stated the stock Porsche LSD's are weaker so they sometimes break and the friction plates wear out very quickly so after a few months they become basically an open differential. He told me the theirs should last at least 2 years with heavy use but they have seen quite a number of them still ok after 5 years of racing. I'm still on the fence about getting one at all. I just had the whole tranny rebuilt, and do not want to have to tear everything apart again. I will probably wait till later in the year and buy one then keep it around for the next time the engine has to come out for something else.

Geoffrey

The preload exists only as an assembly measurement. When the diff is operating, the shaft presses on the ramp angle and presses the plates together which limits the slip. The preload is a small percentage of torque than the overall assembled package while it is working. The steeper the ramp angle (40 vs 80) will press the disks harder together.

Rob S

I found this write up that I'd saved long ago. I can't confirm its source or vouch for its accuracy, though it seems to make sense. It answers how one can speak of percentages with respect to locking factors -- I think there's lots of confusion about this.

MikeD94

While on the subject of differentials, is there such a diff for 930's similiar to "Torsen" diff's? It's the type of diff that uses worm gears.

kens911

yes the torque biasing diff . Quaife made the gleason torson differentials. the guard version works the same but is supposed to be stronger. Back in my younger days I was considdering putting those in a Jeep cj that I had stuffed a chevy V-8 into but didnt because a lot of people were breaking them. now 20 years later I still hear the same thing about quaife differentials.