Re: Posi Unit


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Posted by Dan Shockley [12.2.142.13] on Tuesday, January 18, 2011 at 03:18:14 :

In Reply to: Re: Posi Unit posted by Warren Duchesne [74.241.226.141] on Monday, January 17, 2011 at 13:57:12 :

Warren,

I am all for alternatives, so if you get enough interest, go for it!!

However, I disagree with your comments above. A clutch type limited slip "posi" differential requires some traction on both tires to operate. You will find that on ice, for example you can spin one tire without spinning the other. This is because of the shaft/ramp design of the limited slip, they require resistance on both tires in order to apply torque to the crossshaft, thereby applying pressure to the clutches and locking up the axle.

A detroit (I have one in my 1959 WM300), true trac and lock right (I have one in my land cruiser) operate positively without a traction requirement on either tire. They essentially operate on the principle that neither tire can spin slower than the driveshaft input. If one wheel slows to that speed, the positive clutch engages. In order to differential, these lockers always allow the outside tire to overspeed the differential.

The autolocking differentials offer superior traction and are lower service than clutch type differentials. They can, however, exihibit unusual handling characteristics. And, can be downright dangerous on ice because the differential can "push" you in a straight line despite steering input.

That said, you are absolutely right about the advantages of OEM type Posi units. They offer seamless operation, no handling side effects (this is the reason that the OEM's favor them) and no input from the drivers seat.

The ARB lockers have been available for 4 years. I have sold 175 units, but am currently sold out. I would be happy to discuss offline.

Thanks,
Dan
dshock59@yahoo.com



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