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?

 

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.

 

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