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Discussion Starter #1
2005 OBW w/4EAT here.

I have a strange issue:
When accelerating at normal speed from a standstill, the car will have a slight 'bounce' immediately after it shifts from 2nd to 3rd. I have come to the conclusion that this must be an AWD issue. From what I understand, the 4EAT will shift power from all 4 wheels in 2nd gear ---> to 90% front wheels in 3rd gear.

If this is truly the case, then what part of the AWD system is responsible for easing that transition? Is it the transfer case or the actual transmission itself? (I know that they are housed together... just trying to narrow it down)

THanks.
 

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seems unlikely to be torque bind but, go to a large,flat,dry,paved parking lot and see if the car can do 'donuts' while at idle. If you feel a lot of jerking, or need to goose the accel. pedal to get the car to move - you have torque bind. 2-3 sources for that problem.

and, use of the FWD fuse in the box under the hood can help track down TB issues.


got any other info on the car? miles, maintenance, has the tranny fluid ever been changed, etc.
 

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From what I understand, the 4EAT will shift power from all 4 wheels in 2nd gear ---> to 90% front wheels in 3rd gear.
This is not correct, but is widely circulated, repeated and believed to be true. The AWD clutch is, essentially, continuously variable, and is controlled according to a number of parameters, including gear, speed, throttle, engine load etc. In 1st gear, and somewhat in 2nd, the clutch control responds at a more rapid rate to some of these parameters than in the higher gears, but neither 1st nor 2nd will necessarily set a full-time, 100% engagement of the clutch.

How did you come to the conclusion that it's the AWD? Did you insert the AWD disabling fuse to see what happens with it in (and the AWD not active)?

Perhaps a more detailed description of what is happening would be helpful. How we think of a "bounce" and what you're experiencing might differ in as many ways as there are readers here.
 

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Discussion Starter #6
Thank you for the thoughtful responses.

1 Lucky Texan: I attempted what you suggested. It does seem to have the symptoms that you suggested. Quick info on the car -- 78,000mi. Been in the family since new. I very recently got it as a hand me down from my sister. Other than regular M1 oil changes, not much has been done to the car. Typical maintenance stuff like cv replacement, battery replacement, tires, iridium plugs, etc. Nothing big. I don't think that the trans. fluid has ever been changed.

cardoc: I will check the fluid quality and level tomorrow.

plain OM: I was hesitant in writing the 2nd to 3rd 90% thing. You're right that I stated that based onwhat I've read on the net. I was also skeptical about it and figured someone like you would step in and spill the beans. To answer your question, I did not mess with the FWD fuse... yet. The best way I can describe the bounce is that it happens about a half second after the transmission engages from 2nd to 3rd. It jerks. It's almost like a stutter, though without a loss of power.
 

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Probably a good idea to try inserting the AWD fuse (which should disable the AWD making the car FWD) and see if the symptom changes/disappears. This might help identify, or eliminate, the AWD system as a cause.

Incidentally, the 2005+ has the updated 4EAT Phase II transmission in which the AWD system default (failsafe) is FWD rather than full AWD as on previous versions. (This applies when there is a fault in the control system, such as an open connection between the transmission control module and the AWD solenoid.)

A question: Do any of the instrument panel warning lights, especially "AT Oil Temp", "AWD", or "Sport", not light up when the key is turned to ON but the engine is not started, stay lit after the engine starts, or flash at any time?

Also, when you feel the stutter, is there any corresponding movement of the tachometer, such as a momentary drop (other than is normal when shifting to a higher gear)?

Checking the ATF level on the dipstick is a good idea, but other than the fluid being burned (bad smell) or very contaminated (looks black like used engine oil), the dipstick test won't provide an idea of ATF "quality". You would have to draw out, or drain, some to have a better look.

As others have occasionally found, a flush of the ATF sometimes can do wonders (if it appears the cause is in the tranny, but not the AWD). The simplest way is to drain the pan, refill, drive for a short while, and repeat, and do this three times (i.e. three drains and three refills). In some cases a clutch piston or valve is sticking (can lead to poor engagement when shifting) and the fresh fluid is able to clear away whatever is causing the binding. (See http://www.subaruoutback.org/forums/99-do-yourself-illustrated-guides/5843-changing-automatic-transmission-fluid-easy.html?highlight=changing+ATF+easy).
 
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