4wd Acting Up While In 2wd

[blue9q]

Hey guys, I am new to this site, but i've read many of the Q&A's on the forum and I am encouraged. I have a 92 4.3L S10 4WD. Ever since I have had it (2 months), the 4wd indicator had been lit up as if I were in 4wd, even when shifted into 2wd. If your not familier with the s10, the indicator is a picture of your trucks tires, the back are always orange, and the front are supposed to light up when you shift into 4WD. I have spun the tire many times to check, sure enough, it is in 2wd. It does shift into 4 hi, and 4 lo just fine, so i figured it was just a bad light circuit. I hadn't noticed a problem until the other day I was driving up a steady incline at about 40 mph in 2wd, when a grinding noise started. It sounded like a seized wheel bearing, but sounded like it was coming from the transfer case. I looked down and saw that the 4wd indicator (that had always been on) was dimming, then went out. I pulled over and as I slowed down the grinding grew louder, then there was a loud thud, and everyhting went back to normal. The light is still on in 2wd, and I have been able to reproduce this same thing at a low RMP in 5th gear, going up hill...... Why is that light on, and why is my transfer case acting up in 2wd. Could my acuator be causing this? Am I losing vacuum? What?

[95Sierra2500]

I would start by checking fluids in your t-case and front diff for anything out of the ordinary (metal flakes, clutch particles, etc). If you don't find anything there, I would suggest checking your wiring and whatnot - a repair manual would be helpful to you here.