Identifying LSD gear ratio

[Alex]

I know how to perform this trick with a regular diff, i.e. jack the car up at the rear, mark both the wheel and the propshaft with some chalk (etc) and spin one wheel through exactly 10 revolutions, note the number of revolutions made by the propshaft and thus establish the ring and pinion ratio from these two figures. Is the procedure the same for a LSD? What's the best way to do this if the unit has been stripped out of the car? And finally, how do I know if wear on the R+P has gone beyond acceptable tolerances?

Thanks!

Alex.

[60sRacer]

As you described it, you could get wrong numbers on a non-lsd axle. The opposite wheel must be blocked from turning, and the revolutions divided by two. Otherwise the opposite wheel will turn - backwards - some various amount.

On an LSD car, both wheels should turn exactly the same, so just count prop revs and you're GTG, but be sure that both wheels turn OK. I prefer turning the prop and counting wheel revs, but htere's more turning to do - 45 1/2 prop revs =10 wheel revs (my 4.56 diff).

To test backlash, block both wheels or set parking brake, and carefully rotate the pinion flange back and forth; you should feel the backlash. What's good is another question.....

R