Attessa slippage?

[oxford1327]

Anyone have any experience with transfer case or attessa system slippage?
Had car on dyno other day and wheel speeds between front and rear were changing/fluctuating up to 10%over the course of a run.
Atessa system had a complete flush and new fluids installed February last year and has had no issues since then, though in the last month or so the 4wd light has intermittently been coming on at startup then once warmed up tends to go back off.
Any ideas on how to adjust or what to look for would be great.

[GTSBoy]

N2 canister?

[oxford1327]

1 hour ago, GTSBoy said:

N2 canister?

Please elaborate and clarify? 

[Duncan]

well a common problem these days is the nitrogen cannister loosing pressuring requiring the attessa pump to run continuously which may mean the actuator is not fully engaging.

anyway, I don't actually know how fixed the standard system was designed to be. SInce you were on a 4wd dyno, did they mention the concern because other cars they have run on it were noticably more consistent?

Other than actuation issues (you would expect the computer to want max front torque on a dyno because it is 100% wheel slip), they are basically an auto trans inside with wet clutches so it is possible there is a mechanical issue in the transfer case too like worn clutches.

I'd have to say that if my street car had 4wd varying by 10% in extreme conditions personally I wouldnt lose a moment's sleep. Different in a race car or if you genuinely need a perfect 4wd system for regular snow driving or something,

[oxford1327]

3 hours ago, Duncan said:

well a common problem these days is the nitrogen cannister loosing pressuring requiring the attessa pump to run continuously which may mean the actuator is not fully engaging.

anyway, I don't actually know how fixed the standard system was designed to be. SInce you were on a 4wd dyno, did they mention the concern because other cars they have run on it were noticably more consistent?

Other than actuation issues (you would expect the computer to want max front torque on a dyno because it is 100% wheel slip), they are basically an auto trans inside with wet clutches so it is possible there is a mechanical issue in the transfer case too like worn clutches.

I'd have to say that if my street car had 4wd varying by 10% in extreme conditions personally I wouldnt lose a moment's sleep. Different in a race car or if you genuinely need a perfect 4wd system for regular snow driving or something,

Ahhh OK thanks for the clarification, the attessa system has sort been one of those mysterious gadgets that I didn't wanna stuff with too much while it's working, the old "if it ain't broken"... 

I'm guessing that the amount of slip was noticeable enough to them to have said something, and they've done plenty of GTR and Subaru stuff on a regular basis to have made a note of it, hence asking the question if it is something that can be adjusted for future reference. 

On the road it has not been noticeable at all, as in it do not effect drivability in the wet or stuff like that and the 4wd light on dash doesn't flash etc, so not showing a code to diagnose and that is annoying 

[Duncan]

Personally, I wouldn't be spending my hard earned on for a daily driver unless it was causing a noticeable problem...

Something not working fully could have a lot of causes, most of which come down to age/wearing out but not having failed yet.  Since the problem is somewhat intermittent it would be hard for a knowledgeable mechanic to track down, let alone someone without familiarity with the systems