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I have an '01 Outback (manual) with 210,000 miles. The engine runs strong (good compression) and smooth. While I'm driving sometimes it feels like a gusts of wind is hitting the car (but it's not windy). It's a subtle on and off resistance and is most noticeable while driving at a constant speed. While this is happening the engine runs without hesitation. at best I can get 23 mpg highway.

Additionally, when I first start driving it will roll if stopped on a slight incline/decline but after a couple miles the resistance kicks in and it will not roll on a slight incline/decline. When rolling to a stop (in neutral), it will come to a more abrupt stop (in the last few feet if coasting to a stop) than what is to be expected from a manual.

I've checked the brakes and they don't seem to be the culprit. When on a lift the front wheels spin easily while the back require significant effort to turn. The wheel itself moves easily as far as the play (1/18 of a turn or a couple inches) in the axles and rear diff . I'm not sure how easy the rear wheels are suppose to spin or if this a measure of anything.

Either way, some days it feels like I'm pulling a small to mid-size trail and the mileage is reflecting that.
 

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Hmm? Thinking release bearing but pretty sure with car in neutral and release bearing failing you'll actually get the car to creep given the bearing cause enough friction you get some transfer of power to the gear box still.

01 - could be some type of issue with brake pins hanging up and holding brake pad pressure on the discs. Whats the story on the gear box oil change and diff gear oil?

Have you checked the wheel bearings?
 

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can it maneuver without jerking in tight parking lot turns/figure-eights? Even after warming up?

Could you check hub and brake temps after a long drive with an infrared therm.? compare side to side. Has the driveshft bearing and u-joints been examined?
 

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I think 1 Lucky Texan might be on the right track, in this case, a center differential viscous coupling (VC) that is "stiffening" when it warms up.

However, if the "gust of wind" symptom shows up when travelling straight, as seem to be the case, then there is yet another factor -- the tires. Are they all the same brand, model, size and tread depth?

If the VC is malfunctioning, it won't have a significant effect when going straight except if the tires aren't the same. In this case, torque bind ("jerkiness") can build up in the drive train even when going straight.

I'm also interesting in the wheel turning comment (when the car is up on a lift). There should be little or no difference in effort required to turn a front wheel or a back wheel (assuming the car does not have a limited slip rear differential).
 

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Discussion Starter #5
"Whats the story on the gear box oil change and diff gear oil? Have you checked the wheel bearings?"

I'm sure the gear box and diff oil could use a change. I've had the car for a couple months and don't know the history on it. Even if it's due for a change, would it cause this type of problem?

can it maneuver without jerking in tight parking lot turns/figure-eights? Even after warming up?

"Could you check hub and brake temps after a long drive with an infrared therm.? compare side to side. Has the driveshft bearing and u-joints been examined?"

-No jerking or noises in tight turns. Drive shaft/u-joints replaced a month ago but not sure on drive-shaft bearing. Additionally, there is no bearing noise or really any noise at all even at slow(quieter) speeds. I don't have a infrared therm but that is a valid point. I thought the brakes might be getting hot but there is no brake dust build-up or visible sign of excess wear.
 

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Hmm?
Could it be engine loosing power old plug wire or something acting up and some power loss and not be anything related to drive lines or bearings?
 

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Discussion Starter #7
I think 1 Lucky Texan might be on the right track, in this case, a center differential viscous coupling (VC) that is "stiffening" when it warms up.

However, if the "gust of wind" symptom shows up when travelling straight, as seem to be the case, then there is yet another factor -- the tires. Are they all the same brand, model, size and tread depth?

If the VC is malfunctioning, it won't have a significant effect when going straight except if the tires aren't the same. In this case, torque bind ("jerkiness") can build up in the drive train even when going straight.

I'm also interesting in the wheel turning comment (when the car is up on a lift). There should be little or no difference in effort required to turn a front wheel or a back wheel (assuming the car does not have a limited slip rear differential).
The wheels are all the same size and make with only a couple thousand miles on them. The resistance in the rear wheels when on a lift seems to come from the transfer case/transmission. I say that because when I move the rear wheels back and forth, the "play" is smooth and easy through the drive-shaft until it hits the transfer case area. i.e. the rear drive shaft and diff seem to move easy for an inch or so.
 

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Discussion Starter #8
Hmm?
Could it be engine loosing power old plug wire or something acting up and some power loss and not be anything related to drive lines or bearings?
That's a good point. I recently replace plugs, wires, air-filter, belts, etc. The reason I hesitate to think it's the engine is because at times the engine pulls real hard during aggressive acceleration but then this "resistance" kicks in. The engine doesn't bog down or shutter. It also has a new fuel pump and filter. Normally when I've power issues it's been a noticeable engine behavior, i.e. pinging, rough idle, or what-not. But those symptoms are not prevalent here.
 

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Leaky vac hose? Power when accelerating then power loss when you back off on the throttle could be fuel related or vacum leak related.
 

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Leaky vac hose? Power when accelerating then power loss when you back off on the throttle could be fuel related or vacum leak related.
Potentially, but there is still the issue of shorter rolling distances and hard to turn rear wheels when on a stand.
 

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I'm still leaning toward a drive train issue, and like others, wondering about the rear wheel rotation stiffness. Which brings me to:

Drive shaft/u-joints replaced a month ago but not sure on drive-shaft bearing.
Was this before, or after, the problem being discussed appeared?

Incidentally, it's interesting that you were able to have the U-joints replaced. The Subaru propeller shafts aren't designed for easy U-joint replacement and only a relatively few shops are able or willing to do it. If the problem began after this work was done, perhaps one of the joints is defective and is seizing, especially after some driving. The same could be said for the carrier bearing.
 

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Discussion Starter #17
Was this before, or after, the problem being discussed appeared?

Incidentally, it's interesting that you were able to have the U-joints replaced. The Subaru propeller shafts aren't designed for easy U-joint replacement and only a relatively few shops are able or willing to do it. If the problem began after this work was done, perhaps one of the joints is defective and is seizing, especially after some driving. The same could be said for the carrier bearing.
I'm not certain if the problem was occurring before the drive shaft (entire shaft w/u-joints) was replaced. I wonder improper installation would cause this type of issue. It was a reputable mechanic that did the work. I changed tranny and rear diff fluid and neither had metal chips in fluid. Additionally that did affect the problem.

The wheel seems to move back and Fourth easily but seems to encounters resistance in either the rear diff or transmission. It's hard to pinpoint but it's obvoius the brakes are not the culprit and I'm less certain its the diff which means it's more likely to be in the vicinity of the tranny.

Any ideas? Could it be a bearing without any bearing noise?
 

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Could it be a bearing without any bearing noise?
I would imagine it's possible, but don't want to jump to conclusions. At this point there's a drag on the rear drive, but we don't know for sure if it's in the transmission, and being manual transmission, I'm not sure if that might be a normal characteristic -- I sort of doubt it, but would need someone with a manual to verify.

I guess the drive shaft could be disconnected from the rear differential to see if the rear wheels and rear differential turn freely (more than just a part of a turn); that could deal with one uncertainty.

Incidentally, when turning one wheel it's most common for the opposite wheel to turn the same amount in the opposite direction. This is especially the case if the transmission cannot turn, i.e., it's left in gear with the engine off. Did you observe this?

Quite puzzling. Have you considered taking the car back to the mechanic, especially if the problem seemed to appear after the driveshaft was replaced?
 

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Discussion Starter #19
I'm not sure if that might be a normal characteristic -- I sort of doubt it, but would need someone with a manual to verify.

Quite puzzling. Have you considered taking the car back to the mechanic, especially if the problem seemed to appear after the driveshaft was replaced?
I wasn't sure if this type of resistance was normal for a manual. I plan on taking back to my mechanic and having them trouble shoot for me. They'll probably have a better idea of potential culprits.

"Incidentally, when turning one wheel it's most common for the opposite wheel to turn the same amount in the opposite direction. This is especially the case if the transmission cannot turn, i.e., it's left in gear with the engine off. Did you observe this?"

Yes, everything seems to function "normally" just with resistance.
 
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