Engine/Transmission (1994 - 1998) 4wd engage on axle

[Jgolden]

Have mercy, I usually post on the 1stgen forum.

The 4wd on my 98-2500(gasser) won't go into 4wd. The transfercase will shift but the front axle engage does not work.

The 4wd light does not come on. What controls or actuates the vacume "motor" on the front axel? There doesn't seem to be a switch on the transfer case shifting lever.

I'll have to get under it again, but thought I'd try to get info before laying in the snow.



Thanks any info

 

[Woodenhead]

There should be a switch on the transfer case that switches the vaccum lines to operate the CAD (Center Axle Disconnect) when you move the transfer case lever. When mine quit working it was a sticking vac. switch and leaking diaphragm in the CAD.

 

[RStankevitz]

my 96 wouldnt work turned out one of the steel lines from the tcase to front end had rusted out the joys of maine winters:-laf

 

[Jgolden]

Thanks for the quick replies. Now I know what to look for. Rusted lines a good possibility. I'll post the answer if/when i get it.

 

[MLee]

Fallow all the vaccum lines and make sure you have vaccum all the way to the cad.

Marv.

 

[DieselDoghouse]

One major source of trouble as mentioned is the CAD motor diaphragm. I still can't believe sucking in water can be helpful so while your working you might want to extend the relief line (Capped with a vent bobbin and strapped to the vacuum harness at the transmission) and carry it up someplace dry like the top of the firewall. Worked great for me.

 

[MLee]

As DD mentiomed I done this right after I got mine. And while your at it do the rear also. You just never know.

 

[Jgolden]

Thanks,All my vents are up out of the way. Too much snow and ice I'm taking it to a shop for fix, but thanks for the education, now I know what to ask when they start to work on it. Must be fairly common the shop knew what the problem was before they looked.

If it didn't have posi I doubt I could get out of my driveway.

Thanks to all.

The salt, here eats all the tubing.

 

[Jgolden]

AS info it was the CAD motor diaphram, the whole assembly crumbled under any pressure. Salty roads year after year. Small leak but enough to stop 4WD engage. Getting the shield off also a pain. The lines were ok.



Is Dodge the only one to use this set up?



Dealer was the only source found for part, at least on short notice, $200.



Thanks for the info on the cure.

 

[DieselDoghouse]

Know what you mean— I replaced the 4 10MM bolts with SS from marine store after one broke off. The vent I am talking about BTW is not a gear box vent but the Relief vent for the vacuum circuit (check your manual's diagram) it is typically strapped to the hard lines coming from the vacuum manifold along the firewall but its WAY DOWN by the top of the transmission — a BAD place fer it. Glad you got fixed.

 

[Jgolden]

On the vaccum vent deal. Mine was extended up under cover on the engine side of the passenger side fender . Thanks for pointing out where it was.

Thanks