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I have a '12 Express with 3.55 gears and LSD according to the build sheet and broadcast sheet. The truck has the new style ZF 245mm rear axle with the drain plugs on the passenger side of the axle housing and no filler plug in the differential cover.

I tested the LSD by lifting the axle up so that both wheels were up and in neutral and rotated the left tire by hand and the right tire rotated in the opposite direction. Then I lowered the truck so that only the right tire was on the ground and I could spin the left tire that was off the ground. So I'm like hmmm what's up with this LSD.

Next I drive to a open asphalt parking lot to do a pavement test. I pressed off the ESP button and then poured water on the left tire and in front of it and the right tire was on dry pavement then nail it which spun both tires. Then I poured water on the right tire with the left tire on dry pavement and nail it and both tires spin. The I do a brake torque on dry pavement and both tire spin and finally I pour water on both tires and in front of them. Then cut the wheels to the left and nail it and do a 360 with both tires smoking.

So I'm confused about testing the LSD, it acted like a open differential with the tires off the ground but on pavement it behaves like a LSD with both tires spinning
even with unequal traction. This must be a torque sensing differential because it will act like a open differential until torque is applied then both wheels spin.

Anybody know what type of LSD they are using for the 245mm ZF axle?
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