service 4wd service light on????

I have a 99 SILVERADO WITH JUST OVER 100,000 MILES....NO PROBLEMS OTHER THAN REPLACING UJOINT AND REAR PARING BRAKES ....
I HAVE CHANGED MY TRANNY FLUID AT 50,000 AND AM LOOKING TO GET IT CHANGED SOON... Yesterday I was driving and the "service 4wd" light came on in the dash. I came on and flashed for about 2 mins. I has never came back on since yesterday. What could this be? Soory about the caps......

sounds like durty connectors. i would clean the ones at the trany.

If it continues to come on, have the 4wd switch checked if its an electronic shifting transfer-case. Mine did the same thing and I had to have the switch in the dash replaced.

remove your 4wd switch and re-solder the pins on the circuit board. A simple task.

I have a buddy that has a 03 and i swapped out his 4x4 switch in the dash with mine and drove it this weekend......same...I stil get the service 4wd on mine with his switch and he does not get this message with my switch...so this deletes the switch as the problem......what next..i was told to clean the connections at the tranny.....where ???? exactly??.. I have a chiltons repair manual and they dont get into the transfer case much at all is it the sensor at the transfer case or the tranny???? any help is appreciated...Also it does come on sooner now....Like after 5 mins when the roads are wet....but about 15 mins or longer when the roads are dry....