2011 "growling" noise and vibration in turn - Subaru Outback - Subaru Outback Forums
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post #1 of 3 (permalink) Old 10-16-2011, 07:53 PM Thread Starter
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Question 2011 "growling" noise and vibration in turn

I have a 2011 Outback 2.5 w/ CVT. Since new, when I am making a sharp turn (around 90 degrees) and accelerating, I get a "growling" or "grunting" noise accompanied by vibration that can be felt in the seat. It lasts until I start to straighten out and goes away until the next turn. The noise and vibration is not present in a slow or gradual turn. Neither is it noticeable in a sharp turn without acceleration.
I have taken it to the dealer a couple of times. They tried "relearning" the transmission with no help.
The Service Manager could not explain it. The next time I took it in he drove several new Outbacks that were on the lot and said that they all did it to some degree. He said that he would check with his Subaru rep the next Monday and call me back. He never did. I called several times for a week and was finally told that he had told the Service Writer to tell me that the rep said that it was "normal".
Well. I have been a heavy equipment Service Manager for over 30 years and it doesn't sound or feel right to me. It feels like discs or clutches in the differential are slipping.
Maybe "normal" just means that they all do it.

Anybody got any experience with this type of noise and vibration on these?

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post #2 of 3 (permalink) Old 10-16-2011, 08:15 PM
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I have an 04 I JUST purchased two days ago and I noticed the same thing. Its my second Subaru in like 15 years but I sure don't remember this noise the last one I had! I'd be interested to find out what it is.

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post #3 of 3 (permalink) Old 10-16-2011, 09:17 PM
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I seem to recall other posts about similar symptoms -- might be worth some searching, especially in the Gen 4 forum.

If it is "normal" (might have been more helpful if you had driven the dealer's cars), there might be an explanation for the symptom, although it doesn't make it right.

The CVT, like it's predecessor 4EAT, uses an electronically controlled, hydraulically activated, multi-plate clutch to transfer power to the rear. The hydraulic pressure on the clutch piston varies in accordance to number of parameters, including engine speed, vehicle speed, engine torque, and throttle position; in the latter case, the more advanced the throttle, the more pressure is applied.

When turning a sharp corner, the clutch has to be less than 100% engaged in order to accommodate the fact that the front wheels turn at a different speed than the rears. Most tight corners are negotiated at little or no throttle, so this combination works. But if the clutch remains fully engaged during cornering, as when accelerating (i.e. with much more throttle), the car could exhibit torque bind symptoms, which are the same as cornering in a 4WD vehicle with the transfer cases locked.

Throttle position for accelerating in a tight turn will depend, in part, on the gear the transmission is in at the time. With the 4EAT, there's only four gear ratios. But with the CVT they're infinite (unless Manual is selected). It might be possible that the CVT gear ratio at the time of the turn is such that for the same degree of acceleration, in some instances more throttle has to be applied leading to increased engagement of the transfer clutch and torque bind symptoms.

This might be verified by recording transmission control parameters with the Subaru Select Monitor while driving the car. The data might identify a high degree of clutch engagement combined with certain CVT ratios.

It might also be possible to test this theory by using the CVT's Manual control mode and selecting different gears when turning. Different gear ratios will require different throttle positions for the same acceleration, and if the symptoms appear when more throttle is needed to accelerate in only certain gears, it would tend to support the idea.

This will only verify if the AWD clutch seems to be engaged excessively when accelerating in a tight turn. The solution might be in changing the programming for the CVT gear settings, or modifying the relationship between the input parameters and clutch engagement. Both would require Subaru's involvement, but at least knowing what is happening might be a start.

Be interesting to find out if this is what is happening.
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