I have a 2001 Dodge Ram 1500 4x4. I can not get it into four wheel drive. The forward propeller shaft turns, but there is no vacuum to the front axle shift motor. I have tried two vacuum switches from Autozone. I have Vacuum on the white line to the vacuum switch, but nothing on the red or black lines. I can put it into four wheel drive by using a external vacuum pump to the shift motor on the front axle. Where do I go from here?

 

Measure how much vacuum you have on the white line.
You should be able to rent a vacuum gauge or if you know someone who does motorcycle stuff you can get them to read the in/Hg for you.
Or, check up the line length and make sure it's not sucking air someplace.

 

The metal lines like to rust, and break. If you have vacuum at the switch, but, not getting it to the front axle, the problem is somewhere in between. Verify you get vacuum where the soft lines hit the metal lines just in front of the t-case, if you have vacuum there, the metal lines are likely your problem.

 

I took the connector off of the top of the transfer case's Vacuum switch. I introduced a vacuum on the white terminal, then took a small vacuum hose and connected it to the red, and then to the black. The shift fork on the front axle moved back and forth. I then took the vacuum switch out and connected the lines back up to the switch. I depressed the the ball, while introducing vacuum to the white line. The shift fork on the front axle does not move. I replaced the switch once already, i am stumped. Can you get a new connector to hook to the top of the vacuum switch? BTW the switch I am using is a Duralast SW2258.

 

With the switch installed, do you get ANY vacuum thru it to the front axle? Do you have the connector indexed right?

 

I assumed it was indexed correctly, but it may have been worked on before I bought it. I hear some leakage from the top of the transfer case, I thought the plastic block that plugs into the vacuum switch might be hollowed out enough to leak. Do you have the pin out for the vacuum switch, is the connector available if in fact it is leaking.

 

The connector should be 'keyed', if you pull it off and look at it, there should be some flavor of indexing somethingorother on it.

Do you get any vacuum at all to the front axle, on either line?

 

Mine Is Doing The Same Thing Can ANYONE Help?

 

Try "squeezing" the black connector around the vac switch. You might need a helper to check for vacuum at the CAD as you do this. These big black rubber plugs stretch internally like 19 Kids and Counting, then they no longer seal. Actually very common. The right way is a new harness and they're surprisingly affordable at ~$36, part #

52105317ab

The Colorado white trash way (that's me, in case any snowflake was feeling personally accused or offended) is to find a way to improve the seal, I've used heat shrink butt connectors as detailed in Post #9 here:

https://dodgeforum.com/forum/2nd-gen...s-for-4x4.html

I've done the latter in a pinch, and I just did the former on our '02 2500 because I was completely replacing the t-case and had TIME to source parts.

In fact, when I tore into our '02 the previous shop had just lopped the connector off and slipped a short length of vac tube over the hard lines and respective male fittings on the switch. I was surprised this didn't pull apart or kink, but it had worked from ~2009 to 2022.....

If this is not your issue, the smallest piece of sand or grit will clog the lines from switch to CAD. Blow air thru both red and black and see if the output seems to match what you're putting into it....obviously it'll be choked down but if you're dumping ~100psi in and just getting a gentle breeze at the other end, that's not good. I had this happen on a '99 until something shot out and voila! -- normal flow!

 

Lol I agree with the Colorado white trash way...as I myself am Colorado/Wyoming white trash