got a 99 ram 2500 had the 4x4 worked on multiple time now at a loss why it still will not engage shaft is turning at front diff but it still acts like its in 2x4 last mechanic replaced vac lines on actuator " supposedly " is there a way to test if some of those components are bad or the 4x4 light on dash not illuminating part of the problem? it is a manual tran. and manual engage 4x4 my buddy thinks the auto hubs need changed with lock in and it might fix said problem any thoughts or directions?

 

Likely, a vacuum issue. You can download the factory service manual for your year truck via the following link - https://dodgeforum.com/forum/2nd-gen...e-manuals.html

There is a good troubleshooting guide in the manual on how to address 4x4 engagement issues.

 

If you're not getting a dash light it's likely the CAD (central axle disconnect) is not being triggered by vacuum. So, likely vacuum is not getting from the t-case vacuum switch to the CAD, or from the engine (which supplies vacuum) to the t-case.

Note there's also an electrical connector on the CAD which triggers the light, so the lack of a light could be a red herring if there's a wiring or connector problem

Buy an inexpensive vacuum pump and pull the VACUUM connector off the CAD. Applying vacuum to one port will allow the RF wheel to spin free when elevated. The other port will engage the CAD and you'll see the axle shaft spin with the wheel. The dash light should illuminate in this condition, too

 

Yep, gonna be a vacuum issue, or, the bushings on the two-piece axles have disintegrated. Put trans in neutral, t-case an either flavor of 4x4, and see if you are getting vacuum at the cad. Will be on the inboard port in 4x4, outboard port for 4x2. If you have vacuum, but, it isn't switching, bad vacuum switch on the t-case, if you don't have vacuum in either position, that's gonna be a vacuum source issue. I think its a black or white line that goes up to the vacuum feed on the intake, the green line is just a vent, and ends up behind the motor. The metal lines that run between the switch, and the axle, like to rust out, and leak as well.

 

Pull the vac lines off the cad and see what you have. If i recall one is black and the other red. One is for 2WD and the other is for 4WD. See if you have vac in 2WD first then go to 4WD. If you have good vac in 2WD then it's probably the 4WD vac line to the switch on the t case. Mine got water in it and it was filled with rust.

 

Mine got water in it, then froze..... Ooops.

 

My metal vacuum lines that ran along the frame rail had rotted out as well, along with some breaches in the plastic vacuum lines. I believe the OEM style plastic vacuum line kit for 4WD is still available for sale.

 

Def sounds like a vacuum issue, i changed my cad out with a posi lock kit and i never looked back haven't had any issues yet and i use my 4x4 a lot

 

Somebody produces a one piece shaft to eliminated the lockout. I'm not sure if the one piece shaft from late model D60 axles is a direct swap or not. One of the first things I do personally is take the actuator off and you can flip the snap rings on the plunger and it holds the collar over all the time. Basically eliminate the CAD system. Its unreliable and annoying in my opinion, maybe save .5mpg over the life of the truck. Just make sure your front driveshaft is in top condition, as the the constant rotation will be more likely to cause problems.

Don't waste any money or time trying to replace "auto hubs" there's no such thing on these trucks, unless it has an aftermarket lockout conversion, you'll never find any type of locking hub.

 

I've never really had a problem with the cad system... It's more reliable than the thermal system GM used for a while. (yeah, lets use a heated actuator, that gets buried in snow, and disengages.... yeah, that's a good idea...... somewhere....) Granted, as they age, they require some attention, but the system on both my trucks worked perfectly once I had them straightened out.