The switch is getting battery voltage. Next step is to see if the switch is getting ground from the TCCM when 4WD is selected. Unplug the electrical connector at the switch. Multimeter range set on "VDC 20". Hold the red test probe to the brown wire terminal in the harness connector. Hold the black test probe to the grey with a black trace wire terminal in the harness connector. Now you'll need an assistant to: start the engine, at idle in park, select 2WD, then select 4WD and read voltage. It may show battery voltage then drop to zero, so watch closely. We're looking for battery voltage, either momentary or constant, when 4WD is initially selected.

Plug the electrical connector back into the vacuum switch. With the engine at idle, unplug the vacuum connector from the switch, is there manifold vacuum on one of the vacuum lines?

Post the results of both tests.

 

Ok so I went and picked up my 4wd selector for the dash today and found out the old one was constantly sending 4hi signal. I also replaced about 1.5 feet of vacuum hose that previous owners tried taping and the 4wd def works now. I went and tested it lol. But it's still making the grind in 2 or 4 just not so loud. But now it's making a rattle type I noise to. Kinda like a metal ball is bouncing around in something. I'm so lost with it i might be taking it to a 4x4 shop.

 

Have you removed the drive shaft? Possibly a binding universal joint? Tough to tell without actually hearing it. You mentioned it's not rpm related, is it speed related, like wheel speed? At what speed can you start hearing it?

 

Ok so I discovered the noise. My transfer case was almost 2 quarts low. Filled it back up and no more noise after I spent another $500 in parts, lol that's my luck but 4wd is working great and no funky noises anymore!! Yay!! Thankyou for all your help you have helped me multiple times now.