Hard-to-diagnose, swishing drivetrain

ocalhoun

My '97 Jeep grand cherokee (4x4 all-time) has developed an odd noise lately.
Its a rythmic swishing sound that repeats at a rate relitive to the speed of the truck. Because of that, I know it has to be somewhere on the drivetrain further down than the transmission.
That leaves:
-Transfer case
-Middle differential
-Front and back differentials
-Driveshafts
-CV joints (Recently replaced, and not the cause of the noise)
-Brake system (recently thoroughly inspected, including parking brake)
-Wheels
-A few other parts
The noise seems to be coming mosty from the passenger's side, but that could be a trick of the acustics. Also, if I drive slowly (<15mph) for a while, it will stop swishing and start squeaking.

Does anyone know what this might be?

lysdexia

i would hazard a guess that the swishing and the squeaking are 2 seperate noises. the squeaking would go away at higher speeds as drivetrain speed increases as the moving parts would be moving at too high a speed to actually create the noise.

as for the swishing noise, it could be that one of the driveshafts, probably the tailshaft is either out of phase, out of balance, or the centre bearing in it is dying. the latter is the most likely cause. to test for this, get under the car and move the driveshaft by hand. with the habdbrake on and the car in gear/park, you should not be able to move the shaft at all. if you can rotate it slightly, its probably the universal joints in the shaft one. if you can move it up and down then its most likely the centre beaing in the shaft that has gone.