So I jumpered the 4x4 Indicator light switch and sure enough it's bad. I ordered a new one and will be installing it tonight or tomorrow. That only solves the light issue though. I still have a light rattling noise when in 4x4, so looks like it was two issues.

 

Do you have 4 jack stands? If so, jack up the truck (front and rear) and put two jack stands under the front axle and two jack stands under the rear axle. Open the hood, start the truck and put the truck in gear. Operate the throttle under the hood and listen closely to see where the noise is coming from. May need one other person under the truck to help pinpoint the noise.

 

So I replaced the 4WD indicator sensor (the one that controls the dash light) and the dash light still doesn't work. Would the U joint being bad cause the indicator switch to not work?

 

No. U-joints have nothing to do with that. Are you getting vacuum down to the actuator on the front axle? Does vacuum switch ports when you shift the t-case?