awd light and clicking

service awd light came on the other day and now when start car up 3 or 4 clicks can be heard from somwhere on passenger side of car. have found out if hit brake peddle almost same time as starting car there will be no clicking and light will not come on, if hear clicking light will come on, if no clicking light will be off. have a feeling it's transfer case motor? if so how dieeicult is it to replace and is it hurting anything doing this? it's a 2000 bravada with 4.3l engine.

I would like to bump this up. I have had this same problem, too for about 6 months now. Car still drives fine, though. Any thoughts???

The computer needs to be scanned with an AWD capable scanner like you'd find at a good general auto repair shop or dealer to determine exactly the trouble.
The transfer case fluid needs to be replaced with the GM Autotrak II blue fluid then drive the car a few hundred miles before looking for improvement.
I have all 4 tires the same size and run 32psi front and 30psi rear to try to maintain the same circumfrence and minimize uneven driveshaft speeds.