I'm looking for info on now rear axles work with discussions on posi-traction and limited slip. I have a 69 Camaro with a BU coded axle; ie. 3.73 with positraction. I also have a Ford Explorer which has 3.73 and what Ford calls limited slip. On both of these vehicles with the rear wheels off the ground I count about 3.75 turns of the drive shaft for one turn of a tire. In addition as I turn one tire by hand the other rear tire will also turn. This all makes sense to me. What is confusing me is what I've been reading concerning non-posi units where the drive shaft has 1/2 the number of turns. Can someone point me to a good site which will explain to me everything I ever wanted to know about these things?
Thanks,
Mark

A) I think someone is blowing smoke up your butt on this one - a turn is a turn - what difference does it make if it's posi or not?

B) Everything inside the posi unit is magic.



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Scott
'69 400SB, Richmond 5-speed
'99 HD Road King Classic

I think what Mark is refering to is,to figure out your gear ratio on a non-posi rear end,you turn the wheel 2 times and count the drive shaft rotations.As opposed to turning 1 time with a posi.I've read that on this site also,but never tried it,so I can't verify that it's true.

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67 RS RAGTOP # matching, 4X4 CHEVY TRUCK

Hey guys,

An open differential (non-posi) will turn one wheel twice as fast if the other wheel is still on the ground. If you jack up both rear wheels of an open diff with the tranny in park, and turn one wheel, the other will turn backwards. It has to do with the spider gears in the diff. To check the rearend ratio, jack up one rear wheel, turn it two revolutions, and count the turns on the pinion yoke. This will give you your ratio. On a posi, however, you wont be able to turn one wheel if the other is still on the ground (depends on how strong the posi is), so you have to jack up both wheels. If your posi will turn with one wheel on the ground, then do the same as for the open diff. This is why you don't want to spin your tires around a corner with an open diff, because the spinning tire is going twice as fast as the speedo says, meaning if the speedo says you are going 100 mph as you are spinning one tire, it is actually spinning fast enough to go 200 mph!!!! This can shred tires and blow out spider gears very quickly. Hope this helps.

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69 SSRS Frame-off Resto
81 Z-28 377ci Drag Car