2000 GMC Sonoma Front Dif Noise

[crossman83]

Hi there,

I have a 2000 GMC Sonoma 4.3l with 140,000 miles on it. Periodically when I'm on the highway and traveling anywhere over 70mph for about 10-15 minutes, I will hear this noise slowly come out of my front differential. If hit the 4WD-hi button the noise will go away, and then if I immediately hit it back to 2WD the noise doesn't come back. When I was traveling 200-300 miles at around 70mph the noise came again after about 30-40 minutes and then hitting the 4WD-hi button made it disappear, but when I went back to 2WD the noise came back. I pulled the truck into a gas station, got out and had my wife drive it foward slowly. I was looking underneath to see where the noise was coming from and the clicking noise was coming from the front differential. I drove all the way to our destination in 4wd to keep from hearing that sound. I wasn't sure what was worse, have the sound go on or leaving it in 4wd at 70mph for 100 miles. Anyways, the next morning the noise wasn't there, but still periodically comes back when traveling at 70mph+ for about 10-15 min. Are the CV-Joints inside the front dif slowly moving into the 4wd gears when going at those speeds, or are the CV-Joints or gears inside getting really hot at those speeds so the metal starts to expand causing the joints to partially engage the 4wd gears? I've changed the rear dif fluid at about 100k, but I've never check my front dif fluid. Could this be old or low dif fluid that would cause this problem?

[bcasper42]

This just started yesterday with my 2001 Sonoma SLE. Seems to get worse when I'm crusing along and then take my foot off of the gas. Like you, putting it in/out of 4WD temporarily quiets the problem, and sometimes it's gone completely.

Your post was back in Jan, so I'm assuming you figured it out and got it fixed by now... What was the issue?

-Brian