Hey guys, well I was just driving my 1994 GMC Jimmy on the highway, doing about 75 mph when I start hearing a fairly high pitched noise coming from the front end... almost like a whine. It was speed-related since when I slowed down the pitch would go down as well. However when I slowed down to about 60 mph the sound got pretty low and then a loud CLUNK came from the front end and it stopped and kept driving like normal. This is probably the 3rd or 4th time this has happened in the past year and a half. I have a feeling its something to do with the 4 wheel drive system. I have the electronic 4HI/4LO button. I checked the lights on the button during however nothing seemed to be turned on. And if it makes a difference, my truck sometimes has difficulty switching to 2 wheel drive from 4 wheel drive; the light will turn off saying its disengaged but you can tell that 4x4 is still on for about a minute after. Thanks in advance for the help!

 

bump... nothing yet?

 

Sounds like the front axle is partially engaged.

 

You think so? This noise on the highway is a rare occurrence... but the 4x4 almost always sticks for a little after disengaging.

 

I would check the cable to make sure that it moves freely. Lubricate it while you are there, working the lubricant into the cable. Then, when it is in 2HI, check for vacuum at the actuator. If there is vacuum at the actuator, the switch on the transfer case is bad.