serountree

OK, I did search the forums for an answer, and while there are lots of responses for a whine, none seem to match my problem so here I am. If there is already an answer for this I apologize in advance for missing it.

92 XJ, 4.0L engine, AW4 transmission, NP242 transfer case, all stock. At around 30mph I start to hear what is best described as a 'vinyl sounding' whine, like something is rubbing against a wheel. Inspected the driveline, brakes, and wheels, no evidence of rubbing or abnormal wear noticed. Checked all fluid levels, none found to be low. Sound will increase and decrease with speed, (not tested above 40mph yet) but does not change when turning.

This only was noticed in the last couple of days, and aside from the noise the Jeep appears to be behaving (for values of 'behave' for Jeeps). When I checked the fluid levels in the differentials and transfer case, the fluid did not appear to have any metal particles in it. No evidence of rubbing on the tires, brake hoses or parking cables, driveshafts, or wheel wells.

The noise only is apparent starting around 30mph and with the drivers window down. It is not apparent before that speed, and it 'speeds up' or 'slows down' with the speed of the vehicle. Anyone have an idea of what could be causing it?