Transfer case won't engage 2wd
 

I recently bought a 2001 Dodge ram 1500 all four wheels turn in 4wd however when I shift the transfer case into 2WD nothing engages same as neutral I looked under the truck and the three pin connector that plugs into the transfer case is missing no pigtail for it or anything I got a new plug for it but how do I wire it back into the harness and what does this plug do exactly?

Its a vacuum harness, not electrical. Sounds like the 4x4 system has been modified from stock.... Does the 4x4 light in the dash come on? (is it always on??)

The vacuum switch and harness are intactness on top of the transfer case. The plug i'm referring to is by the output shaft of the t-case it's definitely a 3 pin electrical connector.
https://cimg6.ibsrv.net/gimg/dodgefo...f30e0a9a72.jpg
Vacuum switch (red) is intact. Electrical connector (blue) has nothing plugged into it.

4wd light appears to be functioning properly btw

Red arrow is indeed vacuum switch. Blue arrow is VSS. If your speedometer works, then it is doing its job.

VSS, I see. So that presumably has nothing to do with why the transfer case doesn't engage 2wd. Should I try to adjust the t-case shift linkage or do you think the t-case is f****ed up?

Did you run it with all four tires off the ground, and all four still spin even in two wheel drive? Does the 4x4 light in the dash go out in 2wd?

With all four wheels off the ground here's what it does:
4Hi: all four wheels spin, 4wd light on
2Hi: no wheels spin, 4wd light off
N: all four wheels spin, 4wd light on
4L: all four wheels spin, 4wd light on

Ok I'm guessing you've got a toasted range fork.

I'd first be CERTAIN the linkage is in good shape AND I'd shift it manually with the linkage disconnected. You'll get a relatively positive clunk in each position, may need to use vise grips or pliers.

If symptoms persist I'd plan to pull the t-case and split it open. Also note at some point 2hi may come back, but it likely won't last. Without the shift fork to guide the collar it can just kinda float around.

Thankyou for your insight? I've never pulled a t case or seen inside of one. I've done timing chains/belts, installed motors, steering columns, suspensions, clutches, etc. Is the t-case super technical to pull and fix?