i was driving in 4wd low and the 4x4 light went ouy and i lost 4wd, why did this happen

You can't just drive around in 4low. Its ment for off road use, pulling a boat out of a steep boat launch, pulling someone out of a ditch ect. If you where driving on dry pavement in 4low for a long period of time, you probably did some major damage to the transfer case.

sorry, I guess I should have been a bit more explanatory. I was driving in the lake putting it thru its paces. I just bought the truck and I was testing 4 lo as well as 4 high. I was trying the 4 low creeping thru some snow drifts and all was well. I then shifted to 4 hi and tried the the truch at faster speeds on the plowed ice road, the problem happened about 3 minutes into the 4wd higher speed test

Ahh ok that makes more sense. When you shifted in and out of 4low were you stopped and the transmission in neutral?

yes, and I didn't hear any strange sounds or feel any vibration or grinding, I didn't realize anything was wrong until I saw that the 4x4 light on the dash was out and then of coarse I realized I had no power to the front wheels.

I see, well now you will have to do some fuse, and wire chasing. Start with the fuse boxes and check any of them that have to do with the 4x4(transfer case, switch, actuators, ect). If those are all good move on to wires. See if you have power in and out of the switch. It could be just the switch itself. If that's good then do a visual inspection of the wires, front drive shaft, u-joints ect. underneath the truck. You were off- roading and could have pulled wires loose, got harnesses or connectors wet bent or broke something ect. Hopefully its not a fried transfer case.

thank you sir ! I will do that and let you know the outcome...

Sounds good, I hope its something simple. Good luck n let me know what you find out. Oh also check the fluid level in the transfer case.

thanks! will do...