2nd Gen Non-Engine/Transmission Vacuum problem with 4 wheel drive.

[RNelson]

I can manually engage the 4WD vacuum motor with my vacuum tester, so it's not the diaphragm. Somehow I'm not getting vacuum from the transfer case switch to the vacuum motor on the axle. From what I can tell from the manual, when you shift into 4WD the transfer case will cause the front drive shaft to turn (which it does), and vacuum is supposed to be sent to the inside port of the vacuum motor and vacuum removed from the outside port. Vacuum does get removed from the outside port, but doesn't pressurize for the inside port. That's why I thought it was the transfer case switch.

 

[SnoKing]

So can you hook up the TC switch external to the TC and cycle it by hand? Chris

 

[mwilson]

You probably still have a leak. The only way I can deal with these is to unhook the line from the vacuum pump and hook the pump/gauge unit right there with a longish line so that you can take it into the cab with you. Draw a vacuum, if it holds then start moving the transfer case lever. If it drops to zero when you go into 4wd then you still have a leak. Try the heater controls to get an idea of how quick the needle drops to get a feel for it.

 

[RNelson]

I have not tried to manually engage it from the transfer case, only at the vacuum motor on the axle. There are four vacuum lines coming out of the transfer case switch. Manual doesn't seem to cover how this switch is supposed to operate.

 

[mwilson]

There is a schematic on here somewhere, I'll try to find it. When I bought the '97 I went through this and after about 20 leaks and a new actuator it has worked perfectly since.

 

[mwilson]

Found it!!! A couple of brain cells held hands long enough for me to remember......

http://dodgeram.org/tech/repair/4X4/4x4_engagment.htm

 

[RNelson]

20 leaks???? Really??? Thanks for the schematics.

 

[mwilson]

20 leaks???? Really??? Thanks for the schematics.

I'm serious. Three places alone just for the cruise servo feed. Cracks in lines and boots. Evan had a bad servo on the heater. I finally persevered.

I opted to fix what I had rather than put some kind of retrofit / cable system. The main reason is the wife uses it in bad weather and all I want is for her to pull the lever back, 4wd light comes on and it engages.

Not out of the road because she thought that the 4wd was working.

 

[RNelson]

Traced one of the vacuum lines from the transfer case switch and found the green line was not hooked up to anything. Anybody know what the green line is supposed to go to? I have a picture of it, but can't seem to get it to upload. The green line runs up to an area near where the old lift pump was located.

 

[RNelson]

Found a diagram and the green line is supposedly a vent line. sigh.... http://static.cargurus.com/images/site/2013/10/06/16/31/pic-6527090476046796843.jpeg

 

[RNelson]

OK, think I've finally found the leak. The black line that goes from the transfer case switch to the vacuum motor is leaking on the part that is aluminum (one that runs along the cross member and the frame). Wonder where you find that part? It's not your normal vacuum line.

 

[RNelson]

been trying to find out who sells the steel/aluminum vacuum lines that run across the cross member and frame. Not having any luck. Anybody else ever replaced these? If so where did you find them?

 

[RNelson]

finally found it on www.factorychryslerparts.com. Harness Vacuum Front Axle stock code 52105299. It was about $25, with shipping came to $37 and some change.

 

[Cosmo]

You probably could have picked up a chunk of bulk brake line and bent your own.

 

[JR]

You probably could have picked up a chunk of bulk brake line and bent your own.

Yep, that's what I did with both of my lines. Used the copper nickel stuff so I'll never have to worry about it again.