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Torsen Differential, How it works video

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terryrwood

terryrwood

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And Limited Slip by same Author
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jkstang78

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I ever knew how a Torsen worked. I have used all sorts of Diffs over the years. I have a Detroit True track in my Lightning now, I got a full Spool in 91 GT race car. I have used other Limited Slips. The Torsen and True track would be the only ones I would use now on. After looking up the True track it seems to almost be the same desing as the Torsen. I can tell you the full spool sucks and is only good for track use. Driving it on the street is a hand full.

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RTmiata

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That was a good explanation. Kind of had the idea for a regular LSD but no clue about the torsen even though my miata had one. Kind of wonder what it would cost to swap in a torsen in my car.
 

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RTmiata

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yea its expensive will have to do some more research over pros and cons of the torsen vs standard lsd.
 

madweazl

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What limits the worm wheel from driving the worm gear so the diff locks up? The video out lines that it cant, I was just curious as to why.
 

EXP Jawa

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For what its worth, the Torsen in the video is an older-style Type-1 design, which uses the cross-axis pinion gearing. That's not widely used anymore, only the differentials for the military HMMWV are still built with it. There are a lot of minor inaccuracies in the video too, the creator doesn't seem to know the difference between spur and helical gears, and the worm wheel operation theory is something of a myth - it doesn't truly work like that in practical terms.

The Type-2 design is what is used by any other axle application today. This type uses a parallel-axle gearing design, similar to the True Trac (and other brands) differentials in general configuration, though differing in a lot details. The Eaton video gives a general idea of how the gearing interacts.

What neither video does properly, though, is really explain where the slip-limiting comes from. I got into this in another thread, but basically, helical gear differentials are friction devices, just like any other LSD. The difference comes from (obviously) how they generate friction, and the characteristics of how that friction is built. In this type of product (either parallel or crossed axis), the torque applied to the diff case causes the helical gears to generate thrust loads. A force applied to a helical tooth has an axial component that pushes the gear sideways. Also, the tooth to tooth loads of gears in mesh try to push apart from each other, due to the fairly high pressure angle involved. The result is that the axle gears push sideways against the case, and the pinion gears push radially into the case. This is oversimplification, but accurate enough. The beauty of the system is that these loads - and the resulting friction - are directly proportionate to the amount of torque input in the first place, so high torque (when accelerating) means high thrust loads, and high friction locking effect. Low torque means low friction, so the gearing differentiates easy, which plays nice with the ABS and allows good turn-in and low speed maneuvering.

One other note before I have to jump to a meeting - the LSD video shows the traditional "Salisbury" type of plate diff, which is a nice system since it too builds friction in proportion to torque. But that does not apply to the Traction Lok, which dispenses with the split ramp shells and simply uses a spring to pressure the clutch plates. As such, it costs a lot less, but it also always applies the same amount of force to the plates. The friction load doesn't vary much, and it doesn't adjust to changing torque loads. It also lacks the tuneability that the ramps allow.
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