Click sound when put in drive, after cold start only

I have a 2013 trd sport 4x4. I started noticing a couple months ago (start of winter) an audible click when initially going into drive. Only once in a while at first, now 2-3 months in, is frequent enough that I've assessed it to happen when cold only (90% certain). Seems to be only when going into drive, haven't noticed any in reverse.

I've maintained the truck very well. Trans fluid has beef flushed twice at the dealer, both axles fluid changed, i grease my ujoints regularly... every couple years I'd say. Truck has 141k miles now. I was thinking ujoints, but i don't know. The trucks come with spicer joints stock.

Thought I'd see if anybody had experienced that and knows what the likely culprit is. The click sound kinda sounds like hard plastic clicking, not a metal clunk. I've always done my own work when able so I'm pretty savvy if diagnostics. It's not brakes, steering etc, it's directly linked to shifting into drive.... and only noticed when cold.

Update: now I'm leaning towards transfer case. I was playing around trying to see what causes the noise. I tried 4LO and it started grinding, never heard that before. I was hoping a synchronizer was not aligned or something and it would be fixed now, but no such luck. Now it's starting to click when I'm low speed parking lot turns under a load as well.

Thanks for the input!

 

So nobody has said anything. Haven't heard the noise at all this week. Strange, but toyota trucks sometimes fix themselves.

I did change my transfer case oil, fluid looked good, but was way overfilled.... strange, not sure hope that happens. I'm gonna guess it's never been changed even though the dealer said they did, and it was overfilled before install at the factory. Who knows man, in this crazy world anymore...

 

Update to myself.... truck clicked again when put in drive today.... just waiting on a part to break and then I'll know