I have looked on rockauto and cant figure it out.

Must have something to do with shifting or it would'nt be there.

If you know what it is, is it supposed to hold a vacuum?

So I was troubleshooting a vacuum leak and traced it down to that solenoid/junction/switch or whatever it is. The line itself is fine, tested that alone. But when I connect to back to the trans it wont hold any vacuum, as soon as I let go of the pump the dial drops to zero.

 

I think what you are looking at is the transfer case. And the thing you are looking at is the control switch that goes to the front axle to engage and disengage 4 wheel drive. If you are looking on Rock Auto it's called a transfer case switch.

 

Right you are!

So, should that thing hold vacuum, or constantly leakdown?

 

It should hold the vacuum. But odds are that is not where the leak is. Check all the hoses going to it and gong out of it to the front axle.

 

And btw, it has nothing to do with how the tranny shifts,it's only for 4 wheel drive.

 

Well, I took it off of the transfer case and put tape on it, then put the vacuum on the other end up by the manifold and it held pressure perfectly fine, so I dont see how it could be anywhere else. I even reversed the test and got the same results (just in case there was some kind of check valve or something)

 

and btw, whats up with the big a$$ Silverado ad on the Dodge forum!

 

on my truck the metal lines had a hole worn it in when i baught it, the exhaust pipe was hitting it somehow...

pretty weird