Engine/Transmission (1994 - 1998) CAD 4x4 related question...

[PorterS]

I've been attempting to diagnose a no 4x4 issue on my 95'. Transfer case is working. . No 4wd light and no axle engagement. Checked all the vacuum lines and have good vacuum at the connectors on the front axle. Both in 2wd and 4wd... So I pulled the CAD unit out and ran a piece of vacuum line up to the engine. Fired the engine up and stuck the line onto the CAD unit in both ports. I was rewarded with no movement of the CAD fork. Does this mean I have a bad CAD unit? Did I troubleshoot the CAD correctly? Verified I had good vacuum coming from the line I pieced in, but received no fork movement in either port on the CAD. . Any help appreciated.



How much does a CAD unit cost? Are there any other options instead?

 

[HEMI®Dart]

PorterS,



I have no experience w/ the cad actuator (except for R&R for axle seals) but my guess would be a a tear or hole in the cad diaphragm?



Maybe the Vacuum shift unit can be purchased seperately?



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



About $140 from Quad 4X4.



http://www.quad4x4.com/Dodge Frt Axle&Steering.htm#HUB_&_BEARING_KITS



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[Woodenhead]

I had a similar issue with mine. There's a vaccum switch on the transfer case that switches the vac. on the lines to the CAD. My vac. switch was sticking pretty bad and I also had a small leak in the CAD. Dan at Quad4x4 fixed it up with a new vac. switch and CAD while doing my transmission and it's worked like new ever since.



Mike

 

[DieselDoghouse]

Just take a piece of tubing the the CAD unit (either port) and inhale like a soda straw - you'll be able to tell if there's a leak (probably is). Remember you can replace with a cable actuated posi-lock but as far as I remember you LOSE the 4WD indicator status.

 

[PorterS]

Ok thx guys. . I'll look into it. Just wanted to make sure I was testing the CAD actuator properly. Hope everyone had a nice Memorial Day

 

[JDKammin]

I check mine by pulling it out of the axle, start the truck, and shift the 4x4 lever. It should slide one way in 4x4 and back the other way when shifting back to 2wd. Make sure the wear tabs are still on the ends of the shift fork. I have had these wear out or break and will not let the shift collar slide far enough.

I think your 4x4 light would still work with the cable, as your indicator light sender will still function off the stock shift fork. All you are getting rid of is the vacuum canister.

 

[PorterS]

Well I dug a little further into it tonight. I am getting good vacuum on both lines at the framerail up by the axle. One has vacuum in 2wd the other has pressure in 4wd. Removed the CAD completely and stuck it in the parts washer. Then stuck air to both vacuum ports on the diaphram. The collar would slide both ways just as it should. But, my air lines have about 150lbs of pressure. I would think even with a leaking diaphram 150psi would be enough to move the collar... Took the connector out at the top of the transfer case and blew all the lines out. Seemed to be getting good airflow out of each line... I'm still leaning towards a busted CAD diaphram. If I splice into a vacuum source at the engine the collar will not move. I'm thinking that 15 in. of vacuum isn't enough to slide the collar with a leaking diaphram. Make any sense? Clear as mud isn't it : )

 

[wcjp]

If you're looking at a $140 repair it's definitely time to upgrade to the posilock setup. This also gives you the option of 2wheel low.

 

[PorterS]

With the posi lock setup what do you do with all the vacuum lines at the top of the transfer case?

 

[klaybus]

Does anyone have the CAD vacuum switch part number?



TIA,

Clay

 

[Nate]

You'd just need to block off the main vac line up by the engine and you could pull out all the lines.

With the posi lock setup what do you do with all the vacuum lines at the top of the transfer case?