I just purchased a 2008 Evo GSR with 28k miles. Im planning to do the 30k service soon. I have been searching and reading all the threads about bleeding the ACD/AYC systems after fluid changes, and wether or not it is required. So far it seems that no one knows for sure. Im a master auto tech for a living, and from looking at the service manual and how the ACD/AYC systems are set up heres what I think. From the way the fluid exchange procedures are described in the manual it looks like the drain and refill just replaces the fluid that the clutches sit in, and in any case is not a pressurized system, so there is always going to be a pocket of air above the fill plug. Therefore I think that unless the fluid pump, or lines in the back of the vehicle are replaced there is no need to bleed the system. What do you guys think on this matter?

 

There are two types of fluid systems in the X transfer case and rear differential, hydraulic that need bleeding and simple drain/fill. The hydraulic systems do not need bleeding/flushing/changing at 30k, but you will want to do the drain/fill fluids (see below).

Transfer case: Diaqueen 90W LSD
Rear differential: Diaqueen 90W LSD and Diamond ATF SP III

You'll want to do the transmission too, my recomendation is Redline since the stock GL-3 sucks (IMO). Redline just came out with MT-85 which would probably be good, otherwise you can go with the Redline cocktailX (2xMTL & 1xMT90)

 

I have read that aswell, but I want to change all the fluids just for peace of mind, I do not work for Mitsubishi though so I do not have acess to the scanner, but would still like to do the servicing myself.

Also why do you believe the stock fluids are worse than the redline? Is there any noticeable differences when switching to the redline products?

 

I like the Mitsu Diaqueen 90W LSD for the xfer case/rear diff, but the OEM tranny fluid just doesn't feel very good. Notchy, clunky, grinds, etc. I changed tranny fluid with Redline @ 1,200 miles and it went from feeling like a 20 year old truck to a brand new car...as it should! I hated the OEM fluid since I drove the car off the lot and changed it as soon as I got the chance.

 

Sounds like I will be buying some redline, my trans feels like what you are describing.

How about the fluid bleeding anyone agree or have another opinion?

 

Agreed!

Dont use Mitsu's' stock Diaqueen transmission fluid (GL-3 75-80W)...its garbage (too thin which is why people are complaining about clunkyness and hard shifting). Redline MT-90 is what we use as well to do our services on 8,9 and 10's (would also recommend the GL-4 75-90W from AMSOIL really good stuff too, but a bit more in $$$). The stock Diaqueen 90W is perfect for both the TC and RDiff. You will feel a world of difference when swapping your MT Fluid to the MT-90 (or GL-4) or a cocktail if you choose to do so.

 

The OP lives in Chicago, you may be able to get away with a 75W-90 in the transmission since you're in CA but with the cold winters he will not be able to. I recommend he sticks close to Mitsu's viscosity spec (which I also did) with either the new MT-85 or the cocktailX I recommended above.

 

Ah didn't notice that. Yeah a bit lighter weight fluid would help in colder conditions. Though right now we are having one of the coldest starts to a california winter as I have seen in a long time. Its 47 degrees outside, when its normally in the high 60's to 70's this time of year. Its snowing at low levels (1500 feet) around the areas near my place.

 

How about bleeding or not bleeding the system afterwards, any thoughts?

 

If you change the hydraulic system fluids you will need to bleed them.

 

I talked with Mitsubishi, and it turns out that as I said earlier, the hydraulic systems only need to be bled if a component is replaced, drain refill of fluids for maintenance does not require bleeding. I'm going to confirm with some other sources just in case.

 

when draining the rear, there are two drain plugs. They are marked. You want the one that says gear oil. The transfercase is a simple drain and fill as well. The fill plug faces the pass wheel. It also says gear oil on it as well.

 

I'm talking about the other section of the diff and transfer case the ones that do not take gear oil.

 

Not trying to thread jack, and it is sorta on topic, but is there a good step by step on changing the diff and transfer case fluids, hydraulic or gear oil? Especially valuable if there is a way to do it without bleeding. Please let me know, thanks.

 

Def need to bleed the system if you plan to change fluid. Hydraulic systems + introduced air = No good.