One-wheel peeling. Rear bar too stiff or fried diff?
 

Another autocross yesterday in RI. Car felt great on the PS4S in warmer weather (~70 degrees is warm so far in New England), and new EBC yellowstuffs. I did notice a good amount of inside wheel spin (stock VLSD) on slow corner exits as I was pushing the car harder.

My car has a hotchkis rear bar on full soft, and 8k rear springs. For those that vouch for removing the rear bar, is that for less oversteer or less inside wheel spin? I’m not noticing any excess oversteer, which i know is typically the reason for taking off the rear bar. This is why I’m questioning if the problem is due to my diff overheating/already being fried.

I’ll be taking off a rear end link regardless before the next event, and hopefully that gives me more rear grip and solves this issue.


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Stock VLSD I assume?

If so, fluid within sealed vlsd is prone to overheat. Once that happens, it’ll behave like an open diff.

Rusty has a diff cooler and diff temp gauge, he mentioned elevated diff fluid temperature even just driving around town.

Yup stock diff. Wasn’t expecting to get any overheating on a short autocross run but I guess it’s doable!


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Install an OS Giken with a diff cooler or a Wavetrac. Problem solved. The OS Giken is extremely good. Made a big difference on the Tail of the Dragon.

Your VLSD is done.

Just the good news I was hoping for! haha


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The VLSD uses silicone fluid to operate. The fluid breaks down over time. But it breaks down quicker with heat. The more high heat cycles it goes through. The faster it breaks down. The more it breaks down. The more heat it creates. It's a vicious cycle.

Fixed^


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Stock fluid, too? Or are you running Motul or Redline or something?

The stock fluid boils almost immediately if the car is already warmed up. The VLSD is pretty much worthless because you don't need it for casual driving and it can't handle hard driving you actually need it for :shakes head:

Nope Redline 75W90


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That's what I run. It helps some. Just delays the inevitable a bit longer.

I’m thinking my diff might just be ‘tired’ due to the track use from its past life (prev owner)


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SC’d, track use from previous owner, track use by current owner. Time for new diff mate ;)

And my car only has 30k miles on it… good thing the new Z has a mechanical type diff instead of this VLSD!


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Mine was doing the one wheel peeler at 8k miles. The VLSD is just chit.

I boiled 90 weight twice on the stock vlsd and also toasted it. Then I put 140 weight in the stock vlsd and didn’t boil it again but it was still toast. Seb just installed a wavetrac and we used 140 weight again. As for the diff, it’s insane. You can wot out of corner exit and slide super minimally. Only difference is you have to keep it loaded especially in high speed transitions but other than that I would 10/10 recommend

Its not that it just over heats, that VLSD fluid also wears out and there is no way to replace it. After 50k miles it will work less and less. This fluid is different from the gear oils people are mostly talking about here. VLSD fluid is not serviceable.

:iagree:

The silicone fluid is held inside the ring gear carrier. It's not replaceable. It's separate from the gear lube.