a4WD and whine?

[johnner1999]

have a question...

today it was raining and the roads were a tad slippery so I turned on the a4WD system; and noticed a slight whine from the front end it seems. Not very loud but well loud enough :-) If switched to 2WD or 4WD it seems to go away???

Is this something that I never noticed till now or should I be "worried" :confused:


TIA
John

[Dave]

I personally don't use the A4WD if it is a "tad" slippery but your noise doesn't sound normal. But I wonder why it wouldn't happen in 4HI since the axle defintely has power then. Strange!

[MTPockets]

John, that sounds normal. In A4wd, the shift on the fly actuator engages the front axle, which livens up (back-feeds) the front propeller shaft as well. Basically you run live right up to the transfer case output in A4wd mode. The noise you hear would be a little more front diff noise and the sound of the front prop shaft spinning away.

Joel

[the roadie]

John, that sounds normal. In A4wd, the shift on the fly actuator engages the front axle, which livens up (back-feeds) the front propeller shaft as well. Basically you run live right up to the transfer case output in A4wd mode. The noise you hear would be a little more front diff noise and the sound of the front prop shaft spinning away.

But he said it didn't whine in 4HI, which is identical to A4WD except for the position of the encoder motor on the transfer case and the clutch plate engagement. If the whine goes away with 4HI, the noise might have to do with the torque going through the CV joints or the front diff, but the front prop shaft is spinning in both instances.

If it was mine, I'd support it with four jack stands and run some careful experiments with all four tires in the air. No significant torque that way, but it might be easier to listen for the noise.