High pitch whine - Front diff or belt?

[sturndog]

I have the gas tank sensor problem many people have (fuel gauage not working correctly) but also a high pitch whine when I push down on gas or go up a hill. I am wondering if this is a problem with belt or front diff. No sound from rear diff, this noise is coming from under hood.  Any feedback is appreciated, Sturndog

[Paul]

Are you in 4WD when it happens?

I've heard a whirl up front and called it the front differential. If you're out of 4WD and the hubs are unlocked the front differential ought to be at rest right? With the transfer case in 2WD there's no engine energy going into the front diff. With the front hubs unlocked (back up a few feet after being in 4WD) there's no road energy coming in from the tires.

If it's a belt you should be able to reproduce the sound in park.

[sturndog]

The problem occurs in 2wd, so maybe the belt is old and I believe I heard of a TBS on a pulley related to this. Thanks for posting, I prefer a belt problem over a differential.

[Bobby B.]

On the first gens, it's not uncommon for the bearings in the idler pulleys (those that tension the belts) to go out.  Nissan then charges big bucks for the unit when you can change out a $10 bearing.

Not sure of the set-up on the second gens, but one quick way you can check is to spray some triflow, wd or the like at the pulley center and seeing if the noise went away.  That is, if you can make the noise happen by revving the engine when stopped.

I had an idler bearing go badly on the way to Colorado once.  All I had was a can of Pam cooking spray, which I sprayed on the pulley in the Moab campground.  Got me home quietly.   

[Oz]

How many miles on your X John? There's a TSB on a timing chain idler pulley. Dealer will only replace n/c if its making noise. The replacement part fixes a defect