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Old 06-08-2015, 11:05 PM   #1
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Default OSGiken fluid or bust?

I just picked up a 4.77 Giken from a local TTE partout. Previous Owner says the fluid was fresh this season before he popped a motor and parted out.

I plan to order some fluid and change it when I swap diffs anyways just in case.

Giken 250R fluid is ~$50/liter. Is anybody else running Amsoil or anything else to save some bucks?

Sort of related, what's the consensus on diff mounts. Delrin vs urethane?
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Old 06-08-2015, 11:29 PM   #2
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I started out with Mobil 1 75w140 in mine and had issues with aggressive lockup. I had to be VERY gentle with throttle application on corner exit, otherwise the diff would lock too much and cause oversteer. I thought I needed to pull the diff and adjust plates/springs, but a few people told me I should try the Giken OS250R fluid first. I gave it a shot and it was a night and day difference. It made me faster and more consistent because I could power hard out of corners with no worry of random oversteer.

The only bad thing about the OS250R was that after 2-3 track weekends, I could feel the fluid wearing out and the lockup would start getting too aggressive again. I'm switching to 949's "high-power" diff to see if I can get longer fluid life before the lockup changes. I'm sticking with the OS250R to start, but I'm going to try some Amsoil eventually since it's considerably cheaper.
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Old 06-09-2015, 08:40 PM   #3
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One of the 949 team guys tried a cheaper fluid in his diff. It cooked all the discs, lockup went to zero, and it required a very pricey R&R.

It's a $1600 diff. Don't be dumb
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