I have a 2000 GMC Jimmy with a 4.3 v6, 4wd 2dr. I have had it almost a year and it is my first 4wd. I started noticing a noise coming from my front end two days ago it was a whirring sound, there is also a noise that reminds me of a playing card in a bycicle tire. Also when I put it in 4hi and 4lo about every 15 to 20 feet it feels and sounds like my right side front is slipping and popping. Any help will be greatly appreciated.

 

I'd check the hub/bearing assy. Our vehicles seem to be akin to liking them like a fat kid on a smartie. A whirring sound, to me sounds like a hub/bearing assy. If you have the front on stands & can move the tire top & bottom back n forth or left & right & not see the steering linkage move, it's the hub.
Check the CV joints for excessive play or leakage, twist the front drive shaft back n forth & if it clunks a bit but you don't see odd u joint movement it should be OK. Do the same with the rear drive shaft watching the front u joint for the same indications.
You may also have a vacuum leak that's partially engaging the front hubs.
Just my thoughts & experiences.

 

I have changed my right front wheel bearing with no change I gotta wait to change my driverside. B/c of funds.

Where are the vacuum lines located that I should be checking