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Discussion Starter #1
Came across this which explains things in detail:

Worm and Wheel Limited Slip Differential _ what the IS 300 has with the LSD option

By Kiyoshi Hamai

You've watched the light turn green and then those marvelous streaks of rubber are left behind those Formula One McLarens, Lotus and Ferraris. The rear ends wag a bit, and those two wide strips of molten rubber are imbedded into the pavement. You don't think anything of it, but try that same trick in your Lotus and... no can do. One streak of rubber, but two? How's it done?

You ponder the technical and conclude, Limited Slip differential... That's the trick! Yes, you're correct, limited slip diffy's, but not the type to which we're accustomed. The conventional limited slip diffy often uses friction clutch plates or even welded spyder gears! The avid Lotus nut will have heard about Salsbury limited slip diffy's. These use a friction clutch pack to limit the amount of speed differential between each half of the driven axle. Such diffy's often require special lubricants (all that friction creates lots of heat) and constant maintainance, adjustment and replacement of the clutch packs.

The off roaders and the road racers learned about a new type of limited slip diff that used only gears, no parts that slip, no more adjusting, just drive.

Enter the Worm Gear and Worm Wheel differential. First designed by Vernon Gleasman, then sold to Gleason, who marketed the first of this type of diff under the name of Torsen. Today, there are variations of the basic design being marketed under a variety of names, but the concept remains the same.

The worm and gear diffy unit simply replaces the spyder gears and ring gear carrier. It is a straight bolt in replacement part. But, the results are nothing short of amazing. Gone is the typical spinning of the inside rear wheel when attempting to exit a corner under power. For myself I can see those precious seconds ticking away while I wait for the rear tires to settle down so I can get on the throttle.

With a worm and gear diffy corner exits are smooth, with a touch of oversteer (power induced with BOTH rear wheels spinning!). My speed down those straights are not only higher but, reached more quickly.

Unlike a locked diffy, the worm and wheel diff allows for some differential action. When cornering, the outside wheel of the driven axle must travel a greater distance, thus spin faster relative to the differential housing. However the inside wheel must travel a shorter distance, thus slowing in the same proportion. The worm and wheel diff allows for this action to take place without subtantial resistance.

Now, when a condition is encountered where one wheel on the driven axle has less traction than the other wheel, a conventional differential will allow the wheel with the least traction to spin or increase its RPM relative to the opposite wheel. Unlike conventional diffs, the worm and gear diff prevents the wheel the loss of traction from spinning. Instead the torque is transferred to the wheel with traction.

The situation of corner exits is a combination of loss of traction and cornering. The worm and wheel diff is capable of slowing the inside wheel and simultaneously transferring the power to the wheel with more tractions, the outside wheel.

So, how does all this magic work? Well, honestly it's difficult to explain, but once you get it you'll know (and be hard pressed to explain it to anyone else).

Basically the worm and gear diffy uses a principle of machines; a worm gear can turn a worm wheel, but the worm wheel is not capable of turning the worm gear. The reason for this is the pitch of the gears. LIke a very steep ramp that is easy to slide down but impossible to clumb up, the pitch of the average worm gear is such that the worm wheel can't spin it.

This can be altered. If the pitch of the teeth were altered, so that our worm gear become more like a barber pole, then out worm wheel could spin our worm gear because the gear ratio is not so extreme. It would be like a push-t
 

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Discussion Starter #5
Thanks gang, as you know it feels good when you can contribute
 

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Fun facts to know and tell at dinner parties #1632: Torsen gets it name from the first 3 letters of the words TORque and SENsing. :)
 

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Originally posted by Bruce:
Fun facts to know and tell at dinner parties #1632: Torsen gets it name from the first 3 letters of the words TORque and SENsing. :)
well Duh

what else would it come from? ...a guy's name perhasp.
 

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Discussion Starter #8
One other tidbit. I was taking an engineering class back in '81 while working for GM and we toured the Gleason factory in Rochester NY, they had just started making the TORSEN for use on Jeeps. I think the author in my post confused the name Gleasman with Gleason. Gleason was a company that mostly made gears and such. They had a milling machine, a normal machine shop impliment. However the bed on this "milling machine" was 40' in diameter as opposed to maybe 24"! The operator operated it from by actually riding up on the head of the machine - huge!
 
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