final update on this until i race it:

i had a historically short chat jon@tre, and he recommended the GL5 75w90 NS. he thinks the extreme pressure additives in the GL5 will help with the stiction that causes the clunking in the diff. obviously it doesn't have the friction modifiers of a normal GL5, but I don't think the clunking caused by the stiction in the diff is a good thing.

to be sure, he also gave me a good natured ribbing about being sensitive to noise, but did think that GL4, MT85, MT90 are not enough in built cars.

gonna switch to that, race it, and see how it breaks in further. if at that point it's still sticking too much, i'll send it to him to remove preload, but he indicated that he is also more for having less preload in diffs.

 

When you going to make the swap? It will help me know if I need to swap to MT90 or stick with 75w90NS that I have been running.

 

i think at your power levels, jon indicated to me more or less than MT90 would be the wrong fluid for the job.

to answer your question, soon - not sure exactly when though. are the shifts no good with the NS?

 

we use only gear 300 75w90 in the gearbox and Ls version of it in transfer and rear diff... I never had any shifting issues apart from those that were related to a dragging clutch disc..

 

I just filled my 181,000 mile transmission with Gear 300, and am not seeing any issues. If your location is correct, we have about the same winter climate so user experience may vary?

 

at the moment i've got more access to motul so i'm gonna give that a shot and see if it's got the additives that help with stiction in the diff.

car's been sitting in the garage for a while, map screwed up my order and sent me a subaru oil fill instead of the gaskets i need to put the valve cover back on.

it's always 60 or so in my garage, hopefully that's enough to keep the gearbox happy enough

 

I checked the slave for potential pedal mis-adjustment or the clutch stop being out of adjustment, but found nothing. Exedy Twin. Any suggestions for verifying no dragging clutch? And, if it was that, wouldn't it do it hot too?

 

I got Jon@TRe fluid sheet here infront of me with my new trans. I can’t make sense which of the 4 options he suggests I use. It’s winter now so I am not clear on break in recommendation. Thinking the Redline 140 for track work? 600awhp application. 🤯

Also, anyone run the AYC reflash with track results? I got that done, but haven’t tracked it yet.

 

You mean the ACD reflash?

I've tried the ER reflash on track. I don't have times, but I can say that it's different and I like it better than stock. It wasn't a total game changer for me, but I also think it's money well spent.

I still have a 2nd ACD controller with stock tune for racing in classes that don't allow reflashes. I might try to swap it on a track day next year just to get some back-to-back results.

 

Redline 75w90 NS will be fine.

 

my acd reflash made a difference on corner entry, the car turns better with it

 

I had experienced the same issue on a few cars, all on normal organic clutches, where the 2nd was a bit stiff in town untill we changed to a new clutch.. My theory was that the old clutch plate would warp a bit and drag. Different fluid might have helped, but even with the same motul it would be much much better on the new clutch. Dont have much experience with exedy on evos.. The only exedy twin was on a drift skyline where the plate managed to get a bit of it welded to the fly and ruined the rest of the day..

 

90 for most setups, 140 for yours.

ACD flash is likely the single best handling upgrade for the CT9A. Now I get to compare that to a full custom one...with time lol.

 

very interested what you find. i imagine acd reflash gets 90% of it, and the motec is gonna be marginal gains + the ability to customize just to you.

ive posted this before, slightly OT but: this is a link to a cool article testing motec's center diff controller on their evo x rs (it's a pdf article from an australian magazine)

they tested it on an evo x RS, which does not have AYC (according to this article)

what I thought was interesting was how fast and loose they felt the car was by letting the center diff be open. i'm a big proponent that diffs should be open almost always, except when accelerating, hence the emphasis on 1-way front diffs, and little preload. The rear is ok with 1.5 given how much one of the wheels spends in the air when cornering, plus some added stability in straight-line braking

 

I wont say too much about ACD tunes cause my setup has become pretty beyond-the-norm. But for the ER tune worked great when I was softer and on less sticky tires. As things progressed we got to the point the tune started fighting me to the point we would run it full soft and it couldn't put power down on exit and then stiff and it was binding up mid corner and you could feel it just didn't want to turn, especially tight corners.

We've changed things now to try and open up as much as the steering angle increases and ramp in on high throttle or wheel slip and in braking. Really we want the ACD to almost act like the Viscous diff, just quicker. But for that to work, the front and rear diff both have to be pretty on point.