2001 Dodge Ram 2500 5.9L GAS. Anyhow got into some snow today and not an I glad I have Toyos (2ft feel overnight) because if not I would have been stuck. Anyhow pulled the 4wd shifter and no light and definitely no 4wd. So I pulled the lines off the CAD and I'm getting really good vacuum on 4wd line hmmm so just for sh*ts and goggles I switched the 2wd drive vacuum line with the 4wd one and still no 4wd. I'm a pretty good expert on Dodges (worked at a Dodge Stealership) and am just asking what you guys think it could be. I have yet to test into it as it's snowing here and I'm not even in my state so I am not working in the snow 😂. Anywho the vacuum resevrese don't look too be rotted and the front driveshaft wouldn't turn so it is engaging the transfer case and I have vacuum so I'm thinking maybe the CAD itself need rebuilt? Just asking what do you guys think it could be. Well I'm off to have a few beers so I'm staying next to a bar and can't go anywhere CHEERS!

 

If you have vacuum to the CAD, the diaphragm in it must be ruptured. You'll need a new one. The other possibility is that the fork broke.

 

If you get no dash light also, I'd look for whatever turns that on. It's probably related to your problem.

 

Switch is tripped by the end of the shaft of the vacuum actuator pushing it in. If the light doesn't come on, that means the actuator isn't doing its job. If you hook up one vacuum line to it, do you feel vacuum on the other port of the diaphragm? If so, it's blown.

 

I am going to check the pads on the fork when I take it off.
I'll check that never knew that trick

 

Well found out what it is! I did HeyYou's test and the diaphragm is ruptured. Now on to buy one for $100.

 

Yeah, not inexpensive, are they.......

 

Glad you got it figured out!

 

Thanks!
Yeah sucks you have to buy it in a kit, oh well.