The ACD and AYC fluid is contained within one system and share same reservoir. If you change the AYC fluid (as required every 15k), you are partially change the fluid in the whole system.

 

Thats strange. How come you have to bleed the system when changing the ACD fluid but not the the AYC fluid?

 

Bump for the above question

 

Bump again for above question, and where do you bleed ACD from?

In reading the service manual I've been able to understand replacing engine oil (5W30 synthetic), transmission oil (GL-4 MTF 75W80-90), transfer case oil (GL-5 LSD Oil 90w), rear differential oil (GL-5 LSD Oil 90w), and AYC fluid (ATF); but I was not able to clearly understand the ACD fluid replacement.

 

1) You NEVER need to change, drain, bleed, or otherwise service the fluid in the ACD/AYC pump circuit UNLESS lines where removed, the differentials where replaced, or the system experiences catastrophic failure. Just keep it in between the levels in the reservoir in the trunk. Bleeding the system requires the Mut3 factory tool and costs $$$ at the dealer, the procedure is a real PITA. Evoscan may support this in the future.

2) The fluid in the AYC / ACD pump circuit (fed by the reservoir in the trunk) is ISOLATED completely from the ATF fluid in the rear differential (clutch paks) and the gear oil in the transfer case (both in the clutch pak and the rest of the case). The fluids should NEVER mix.

3) A big thing that throws most people into confusion is that the ACD clutch pak sits in gear oil, and the AYC clutch paks sit in ATF fluid. Neither is pressurized. The fluids just sit there and lube the clutches, there is an air pocket at the top in ALL CLUTCH PAKS.

4) The ACD / AYC Pump (called the "Hydraulic Unit" in the service manual) uses high pressure to activate the ACD and AYC clutches.

5) If you notice the level of fluid fluctuate slightly in the rear reservoir for the ACD / AYC Pump circuits, it's normal. If it becomes completely filled and overflows or it runs completely out of fluid there is a problem, at this point the system will most likely throw codes and warnings.

6) Change your gear oil in the Tranny Case every 30k miles for normal use. Change it every 15k miles for severe conditions and track use.

7) Change your ATF fluid and gear oil in the Rear Differential every every 30k miles for normal use. Change it every 15k miles for severe conditions and track use.

8) Various problems plague the ACD / AYC pump (Hydraulic Unit) but most have to do with something called "Galvanic Corrosion". This occurs when two dissimilar metals with a fluid layer in between them form corrosion. There is no real solution to this problem in terms of preventative maintenance except changing the fluid in the Transfer Case and Rear Differential (gear oil and ATF) more often. DO NOT service/change/drain the fluid in the AYC / ACD pump in terms of preventative maintenance. Keep it at the correct level and make sure it's not brown and smelly (indicates BIG failure) and your good.

 

Is Evo 8 similar, other than the ACD reservoir being under the hood? No need to change and if you do, need a special tool and butt aspirin to bleed the system?

 

^All you need to change is the gear oil in the transfer case (diaqueen lsd). Don't mess with the acd reservior or oil.

 

A snap on solus scanner will bleed the system as well provided is has the correct updates and software in it. I just did it at work. I had to replace the clutch fork on my X and refilled the res and bled it with the scan tool. HOWEVER if the person you are taking it to doesnt know anything about and Evo just got to a dealer and find the "evo" mechanic. To my knowledge they are sent to specialized training for working on Evos.