Why does my 2001 Chevy Silverado HD make a poping sound when I’m in 4wd going up a hill

Thank the for replying I flushed the transmission/ transfer case/ and front differential. And I didn’t find any metal shavings. I’m replacing both front hub assembly’s and Rotors/ brakes as well. And I also ordered the front 4wd Actuator.

Sounds like a lot of expensive parts being used as guessing. That’s my biggest concern here. What if it’s internal transfer case? In that case you’ve wasted a ton of money and the source of the problem is elsewhere. Something to consider. Good luck!

I agree that the money I’m spending may not fix the problem but I believe I’ll benefit from it in the long run. I’ll Pretty much have a new front end with Limited lifetime warranties. ( Preventative maintenance). If the parts I install this week does not fix my problem I will have no choice but to take it to a professional. I can’t determine if it’s the front Differential or the transfer case and those parts are why to Expensive to buy if not needed.

Thank you ( DaveJM) for responding and your opinion I appreciate it.