Tommy J

x3 on the alternator

Nocturnal1

I started hearing the noise about 2-3 years ago, in the winter when it was cold (usually first thing in the morning or at the start of the drive). It's increasing in frequency now and appears to occur at any time (not just the beginning of the drive). The noise does appear to go away when I shift (sometimes need to cycle a few times) into 4WD and back to 2WD. Once I do that, the noise doesn't seem to re-appear during the remainder of the drive.

I thought it was the beginning of IWE problems, so I changed the IWE solenoid (just in case) and one of the check valves. It didn't solve the problem. My IWE's hold vacuum, so I'm thinking the grease in the IWE's might be solidifying and preventing the IWE's from fully disengaging (but it doesn't sound like a grinding sound)??? I have about 75K miles.

I would describe the noise as a mild-deep whirl or rumble sound that occurs intermittently at speeds below 35 mph, sometimes accelerating or coasting. I don't think its an alternator problem as it does appear to go away if I cycle it from 4WD to 2WD, and the sound (frequency) doesn't appear to come from something turning as fast as an alternator.

It could be a wheel bearing. I've manually rotated the wheels and they don't make any noise. It could be low fluid levels in the front diff or transfer case, but if that's the case I should hear the noise in 4WD, not 2WD (assuming the IWE's work). I'm going to wait for the weather to warm up before I further investigate.

Tommy J

Switching in and out of 4x4 could just be a coincidence with the noise going away. I think my alternator noise was inconsistent. It could be a pulley, they come and go. My noise seemed to increase with rpms and went away with a new alt