Need Help with Drivetrain Noises

[Jim C.]

I need suggestions for two (possibly related) noise problems. The problems are with my 2000 Subaru Outback, which has 130K miles of mostly four lane highway driving (40 miles one way to work). The car has an automatic transmission. I believe both noises are related to drivetrain issues.

The first problem is a whining noise heard when accelerating. The whine starts slightly above 5 to 10 mph and increases in pitch as I accelerate. If I remove my foot from the gas pedal and coast the noise immediately goes away but returns as soon as I begin to accelerate again. If I shift to neutral while coasting then rev the engine the noise is not present. Nor is the noise present when in park and revving the engine. I recently had the rubber boots replaced on the front driveshafts because one was cracked. Could this be related? Any ideas what may be causing this whine?

My second problem is a noise that is heard at slow speeds. It sounds like pebbles inside of hubcaps but the car does not have hubcaps. Another description is that of a worn U-joint on a driveshaft. The noise is most obvious as you slowly accelerate from a stop or while braking just before stopping. If I go very slow (walking speed) the noise has a cyclic rhythm.

I've inspected the transmission and differential fluids and both are at the proper level. Any suggestions?

[brus brother]

I had the whining in the 40-50 range and while SOA was busy telling me it was within normal limits (?pinion gear), a clicking developed in the tranny in neutral that required they change out the tranny. This is the third tranny in my 00 Legacy GT. Thank you for extended warranty!

[Suzam]

have you ever changed out the front and rear differential oil? I'd give that a try for the whine as you apply power to the drive train. As far as the click, maybe a CV joint?