Subaru Outback Forums banner

1 - 8 of 8 Posts

·
Registered
2003 OB 2.5L AT
Joined
·
66 Posts
Discussion Starter #1
I have a new to me 2003 Outback 2.5L 4EAT with 150K miles. I primarily drive OB stick shift so getting the feel for how 4EAT behaves is something new to learn.

On another thread, I had posted issues with clicking noises coming from the right rear when coming out of right turns. I had replaced AT fluid as suggested first step in addressing the problem and it seems to have helped significantly. Not intending to hijack someone's thread, can someone give me ideas how to localize Clutch pack or Duty C solenoid. I just want to rule out these components.

If I am to put the car on a lift with the wheels off the ground, how can I localize if a MPT clutch pack is slipping or Duty C solenoid failing. I intend to start the car, put it on drive and verify that only the front wheels are spinning. Try the other forward moving gears and verify that still only the front wheels are spinning.

Can I do this without damaging the AWD ? As I understand, our cars are basically FWD all the time unless the wheels slips and transfer drive power to the rear or front again. Thanks
 

·
Registered
Joined
·
18,168 Posts
As I understand, our cars are basically FWD all the time unless the wheels slips and transfer drive power to the rear or front again.
Not correct. If that were the case, the Subaru AWD would be no different than many other part-time AWD vehicles. With Subaru, particularly the 4EAT, the AWD is "full-time".

The most reliable test of the AWD would be to put the car on a four wheel dynamometer, and measure the torque delivered at the front and rear wheels while braking the dynamometer rollers. If the system is working properly, the front and rear would be the same.

Some just go out to a slippery, sloped surface with a few friends, park on the slope at the lower end, have the friends watch all four wheels, and then press the accelerator down with a view to getting the wheels to immediately slip. If the AWD is working, when one or both the front wheels are spinning, at least one rear wheel should also be spinning. If neither rear is spinning then the AWD is not working properly. (If the AWD disabling fuse is inserted, then only the fronts will spin.)

The control of the AWD transfer clutch is based on a number of parameters, including engine torque. When all four wheels are off the ground, it takes very little torque to turn them. Consequently, and depending on the degree of "drag" due to friction and brake contact, only the fronts might turn, or both the front and rear.

Keep in mind that the AWD only works to ensure that the front and rear drive (pinion shaft to front differential, propeller shaft to rear differential) are turning at the same speed. It does not control side-to-side wheel speed. So one front wheel might be turning while the other is not, as long as one rear wheel is turning at the same time the AWD is working.

Have you tried driving in tight circles (such as in an empty, level, parking lot) with the engine idling and the AWD fuse out? If the AWD is binding (instead of slipping) the car will tend to repeatedly move and hesitate, or not move at all, whereas if the AWD is working properly, at slow speeds and low throttle it should be able turn with steady progression.

Your clicking, reported in http://www.subaruoutback.org/forums/66-problems-maintenance/54168-automatic-transmission-jumping-dragging-thudding.html#post589001, could be the damaged CV axle.
 

·
Registered
2003 OB 2.5L AT
Joined
·
66 Posts
Discussion Starter #3
Thanks Plain_OM, I will try that tight circles and see how it goes.

Yes, I thought the same, the damage CV axle could be making that noise and also the rythmic "thudding" when driving the car at 40-45 mph. I will revisit that noise when I get the axle done. I am leaning to do OEM reman axle (allegedly with neoprene boots?) but checking out MWE and RAXLE options as well.

I am in the process of going over maintenance items on the car, even though the previous owner (I am the second owner) claims it is regularly maintained by the dealer.
As we know quality of work is relative to who did it.
 

·
Registered
01 Outback H6 VDC, 97 GT wgn w/ ej22, 98 OBW w/ej22
Joined
·
1,401 Posts
i have tested my AWD by parking on a wet slippery hill sideways.
if the hill is slippery enough and the hill steep enough, when you punch the gas and the wheels spin, the car will side slip down the hill. if one end of the car does not side slip then those wheels are not spinning.
(i used wet leaves on pavement and it did not take much of a hill to notice the movement.)

please be careful if trying this, nothing close to you front, rear or sides.
 

·
Registered
2003 OB 2.5L AT
Joined
·
66 Posts
Discussion Starter #5
Did the tight circle turns, both going left and going right, the car idles around 750, the hairline mark below 1000 rpm on the tach, the car moves steady and slowly. From a wide circle to almost locked left and locked right. Did the same series of circle turns at light throttle, about 1000-1200 rpm, same behavior, slow and steady. I think it is safe to conclude for now that AWD is functioning properly.

I also tried a series of figure-8's at idle speed of 750 rpm. I don't know if this is normal behavior, there are steering wheel positions on both left and right directions that the RPM would jump to about 1000 RPM for 2-3 seconds, then back down to 750 RPM. I did not notice this behavior doing just the circle turns as above.
 

·
Registered
Joined
·
18,168 Posts
Not sure about the 2003, but on my 07 that's normal. There's a pressure sensor on the power steering pump. When turning the wheel rapidly to make a figure 8, or just turning the wheel when parked, both of which are heavy power steering loads, the sensor signals the ECM and that, in turn, increases the rpm.

Some cars of that generation have developed stiff U-joints in the steering shaft. There's two joints back-to-back just before the shaft goes into the steering rack. These can cause the effort needed to turn the steering wheel to vary as the joints rotate. Check this by raising the front wheels and turn the steering wheel slowly but steadily from lock to lock and see if the effort needed varies cyclically. (If one joint is stiff, I believe the resistance will increase twice for each full revolution. If both joints are bad, it will be every 1/4 turn.)

If there was no hesitation etc when doing the tight circles, then the AWD system isn't fully "on" when it shouldn't be, and that's good. That, of course, is only one part of the equation. The other is: Does the AWD work (i.e. more tightly engage the clutch) when it's really needed, as when the wheels might slip. That's what the "slippery surface" or dynomometer experiments deal with.
 

·
Registered
2003 OB 2.5L AT
Joined
·
66 Posts
Discussion Starter #7
Sorry, took too long to update. Started driving the car again last week. I think the reason why I am concerned with my 4EAT transmission is the car is slow to downshift particularly going steep hills. Having driven manual transmission, I am not used to this. I drive by feel, I shift as I sense the need to downshift or upshift.

I also noticed that sometimes, downshifting is not smooth particularly going to a stop light or going steep hill. Is this typical 4EAT ? Too eager to upshift when going up to speed but unsure what gear it needs to be downshifting ? The other day, going up a mountain pass, I tried to force a downshift by stepping on the gas pedal, the RPM went up to 3000 RPM but still did not downshift. Typical random behavior ?

I have done my first round of AT fluid change, will do another when time permits.
 

·
Registered
Joined
·
18,168 Posts
I don't think it's typical. There are posts elsewhere here about hard shifting, but it's hard to assess without actually experiencing it. Complete a few ATF changes and see if that results in any change.
 
1 - 8 of 8 Posts
Top