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HELP!!! how do you figure of the LSD ratio, any tricks...


Guest Anonymous

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Guest Anonymous

Rotate the ring gear/LSD unit until you see a series of numbers. On a stock LSD at least, in the string of number you will find the slip ratio. I found an early E21 LSD at a wrecking yard. It was a 3.64 as expected, and I was lead to believe that all these early LSD's had a 40% slip, but mine has a 25% slip. I also compared the breakaway torque to 2 other 25% LSD's I have and found the 'slip' to be the same. Rats!! I wanted a 40% LSD.

If you have the LSD on the ground, put 2 of the bolts into the flange on each side of the diff. With a 2x4 (or equiv.) lock one side of the LSD by putting a heavy weight on the end of the 2x4 and the other between the 2 bolts. On the other side, put a 4' long 2x4 between the bolts and place a known weight, like a brick, on the 2x4 and slide it along the 2x4 until the the LSD 'slips'. Multiply the known weight times the distance the center of the weight is away from the center of the flange. If it's a 25% slip, you should get a figure of around 18 ft-lbs or so for a used one. The weight of the 2x4 will add a bit to the figure as well. I've never heard of, or seen published figures for the correct breakaway torque. I believe by definition, a 25% LSD should be (I think) about 23 ft-lbs. A 40% slip should have a proportionally larger breakaway torque figure.

Also, I seem to recall that it is very difficult or impossible to modify a 25% LSD to a higher one, but it is easy to do to a 40% one.

Gil

72 Tii

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Guest Anonymous

The p.o. of my 71 had a "S" type diff. but he ground off the "S" on the side so I am trying to figure out whats inside- it worked out to be a 3.64 diff but looks like it been modified w/ a better slipp ratio. Can anyone help....Thanks in advance

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