short whistle noise from tranny

I have a 99 Grand Vitara (5 spd., 105 k miles), that has started making a very intermittent noise that lasts about a second or so. The noise sounds like a flute, penny whistle, or a short tap on a car horn (without dissonance). It can either be a single tone, or move up the musical scale. It seems to come from the area of the gearshift or transmission. Typically it occurs when engine is at idle, and clutch in, with the car moving, (though it can occur at other times, and is soft enough that perhaps we just don't hear it at higher speeds and with higher engine noise levels). Nothing seems to bring it on, or cause it to stop, and it stays at about the same loudness for the duration of the tone. There are no other symptoms. Typically, no one will be touching the shift lever when it occurs. There are no leaks of fluid from the vehicle, or other signs of problem. The car shifts fine, runs well. The noise seems to be getting more common, but still may only be a few times a day - too seldom for a mechanic to be able to listen for it. Any suggestions as to cause and/or remedy?Puzzled

I just purchased a 2002 4x4 JLX. I also recently noticed a whistle noise from somewhere. I'm interested in finding out what this is also.
Mahalo.

Well, the whistle noise resolved itself into more trouble, and turned out to be a problem with a belt tensioner where the noise got transmitted back to sound like it was coming from the tranny. That is the tensioner for the serpentine belt, and it is not a simple job to replace. Replaced the tensioner twice, then sold the vehicle.

good luck