Project 370Z- Improving Grip by Tuning a Cusco RS LSD!

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A breaker bar is used to set the final angular torque.
You can see why the bolts are marked now!
Next, the the ring and pinion's back lash is checked.  Backlash is adjusted with these select fit shims on both sides of the side bearings between the diff housing and the differential case.  A thicker shim reduces backlash while a thinner shim increases it.  You can start with the stock shim and if you are lucky it will work.
Howard checks the backlash with a dial indicator.  backlash is important as if it is off the diff will be noisy and the gear could wear out quickly.  The Cusco case ended up being slightly thinner so a slightly thicker shim was needed.  If you are keeping the same ring and pinion you don't need to mess with the pinion shim and crush collar which controls pinion depth.
Once the shims were set, the diff caps were torqued down.
We replaced the stock diff cover with this part from Nissan Motorsports.  The diff in a 370Z runs really hot and we have been careful not to run it more than 20 minutes at a time.  Since mechanical diffs run hotter than viscous LSD's we can use the 1/2 quart more oil capacity and the cooling fins on the back.

6 comments

  1. 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?

  2. 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?

  3. 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

    1. 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.

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