4wd service engine light and ticking noise at cold start up.
 

Hi I'm new to the forums and had a couple question concerning my 01 Yukon 5.3l 4wd 120k miles. A few months back I started getting service 4wd light. Now this is my first 4wd transmission so forgive my ignorance. My next oil change I had em flush and replace the fluidin the tranny. Uncertain if the used synthetic. I am not the original owner and purchased the vehicle at about 90k miles. the light went away then next day reappeared. Now the it appears and reappears periodically. I tried resetting by unplugging battery to reset but still getting light. Tranny appears to be running fine fluid levels are fine. Is there something else I should be servicing seeing how this is a 4wd tranny?

Now my second question recently noticed on a cold start a ticking noise. Oil levels are normal and I'm using 5w30 valvoline non synthetic. Now last oil change being cheap I switched from a full synthetic that I had been using for about a year. Could this be what caused this? And what can I do to remedy this. I'm concerned about damaging my engine and want this vehicle to last as long as possible. Any Insight would be greatly appreciated.