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| You can see how the six springs will push outward on the pressure rings which will in turn push on the clutch packs. We have reduced the initial torque by about half. We could still remove two more springs but Cusco doesn't recommend running less than 6. If we were doing a high powered drift car we would put in all 12 springs. |
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| A really cool thing about the Cusco RS diff is that it can be switched from 1.5 way to 2 way operation. A 2 way diff locks equally on acceleration and deceleration. This is handy for drifting or dirt driving like rally where you might want to use engine braking to help rotate the car at corner entrance. When set like this, the car will tend to understeer until engine braking torque is applied like when downshifting. Usually you don't want a car to behave like this strongly for grip driving. In this case you probably want to set the differential for 1.5 way operation. When set to 1.5 way the diff fully locks when power is applied and only locks half way when decelerating. You can set the diff up for 1.5 way or two way operation by placing the cross shaft cams in different ramp locations in the pressure rings. The position shown above is the 1.5 way position. When drive torque is applied the cross shaft cam will push in position to the right and provide an aggressive locking wedging action to the clutches. On deceleration the cross shaft will push to the left and the shallower ramp angle will apply a much more gentle force on the clutch packs. |
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| To switch to 2-way operation the cross shafts are flipped around backwards and moved to the symmetrically shaped ramps. In this way the flatter cam in the cross shaft will provide a pretty strong lock in the drive direction but will also give a strong lock in the deceleration direction as well. So for drifting we would want to set the pressure rings to a 2-way position with 12 springs. For grip driving we would want to go with a 1.5 way setting with 10-6 springs. For a heavy car with big sticky DOT race rubber we would opt for more springs. For a lighter car on street tires, less. Since our car uses UHP street tires we are running less springs. |
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| The Cusco RS uses these flat end plates between the clutches and the differential case. If we wanted to convert our RS to a MZ, if we wanted to have a very high initial torque, we would simply remove the pressure ring coil springs and replace the end plates with Cusco's cone springs. This is very cool! |
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| When assembling the diff we lubed up the end plate and dropped it in the case. |
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| The end plate sits at the very bottom of the case and goes in first. |
6 comments
Thank you for your really excellent explanation of how these components work.
One question: Gear type differentials (Torsen), appear to me to offer perfect distribution of power at all time. They are strong and require essentially no maintenance or replacement of parts.
What is the advantage of the Salisbury clutch type that you chose?
If the car was to be used exclusively on the street, would you have made the same choice?
They work better, torsens are really not that great.
Great write up, what lock rate was selected 60%, 80% or 100% for your build?
A youtube channel mentioned cusco recommended to leave it at 100% and only mess with the spring preload because with lower lock up rates the disc tend to run hotter. is this true?
Hey Mike – would you be able to do a detailed article on LSD tuning in all aspects?
1) Initial Breakaway torque
2) Ramp angles
3) Belleville thicknesses and spring rates
4) Different clutch plate treatments and surfaces
5) Different clutch plate materials (steel/carbon)
6) Tuning with different oils and additives
From the rabbit hole that i’ve gone down, it seems that most people only focus on the initial breakaway torque and that’s it. But having different spring rate bellevilles (cone washers) or stacking these washers also effect the LSD and how it behaves and reacts.
For example, the ATS carbon LSD needs ~250ftlb breakaway torque, but yet it doesn’t cause the wheels to skip/chatter in the parking lot. But a metal LSD with 80ftlb breakaway torque can skip/chatter with small steering input.
Something as simple as removing one of the belleville/cone washers and replacing it with a spacer and setting the same breakaway torque. How will that effect the LSD and driving?
Cheers, Mike
We did a few already, a couple of youtube video too. search is your friend.
We have several, use the search function. Videos too on youtube. We have never tuned an ATS diff before except for drifting and we didn’t like it and ended up going back to a spool.