turfguy

hey guys & gals
having occasional problems with my 99 24v plow truck; installed a new 4wd actuator last fall, & plowed most of the season with it. At the end of the season I had my big tires on it & we got a late snowfall, & the 4wd quit working, & I almost go the truck buried in a ditch. A few weeks later I had the regular tires back on it, tried 4wd in the driveway & it worked fine. Checked & made sure the vaccum lines are still hooked up ok.
2 weeks ago, I was at an auction & went up an off-kilter incline to find a parking spot using 4wd, which I didn't stay in, so then I went into a not-so-firm yard to park; flat ground. A few hrs later I went to leave & 4wd wouldn't engage again.
So I get pulled out & go home. Once I got home I tried 4wd again & its working....... grrrr
Seems like after I put a bit of load on it it works. Then when I restart the truck later it doesn't work. Any ideas?

Andy505

I had an intermittant problem with mine, turns out that the plastic bushing between the two axle shafts was broken.

I replaced that and its worked fine ever since.

turfguy

did they have to pop the diff cover off to get to it?

Andy505

I did it.

Its located behind the CAD actuator. You have to pull the right side axle shaft out. Its a decent amount of work for a little bushing.

Tallguy67

Turfguy,
The vacuum actuated CAD is notoriously weak on our trucks. Have you seen the tiny little vacuum lines we depend on to run that thing?
The first modification I made to my truck was to ditch the vacuum operated CAD and instead put in a manually operated one. It is called a Posi-Lok and I got it from my local 4x4 shop.
The installation was super easy and took about 2 hours. The instructions were about perfect and the kit even included a template for where to drill the hole in the firewall. My CAD is now cable controlled. When I want 4x4, I put the transfer case in 4x4 mode and then pull the handle attached to the cable which slides the CAD collar to the engaged position. By jacking up the passenger side of the front axle I barely even lost any differential fluid when I removed the old CAD actuator from the axle casing and installed the new actuator. I cannot speak highly enough about the Posi-Lok CAD. I think the kit cost me about $200. If you want any more information about it, just ask.

tughillnut

just a thought.when I had no 4wd it was a small rubber 90º vacume line up near the cowl in the engine compartment running behind the rubber flap that was slightly dry rotted.visibly ok but once I switched it out with a good piece of rubber tubing it works fine. just my .02 $

turfguy

Thanks for all the repiles so far; since then I've checked all the vac lines & hoses as best I can; had 2 elbows that were pretty much spongy & rotted- replaced those. Had another line at the firewall with a hole in it- replaced that.
Turns out my vacuum pump was bad too; OMG can't believe how much they want for that. Was able to get a used one & had it rebuilt; now I have vacuum with good pressure but come to find out the bushing in the axle is bad too GAHHHHHH!!!!!!
I'm about this close to putting in a Posi-Lok on this truck.....
now I still have a vac leak under the dash, because I still can't get the heater to shift to the vents or floor. So I've been plowing with my feet frozen & my head baking.......
Maybe by spring when the plowing season is over this POS will be working properly......

Tallguy67

Holy cow turfguy, that is a lot of work. My posi-lok cost about $200 and only took a couple / few hours to install.

turfguy

did you have to take the front wheel off & dig around with the axe shafts at all, ot just bolt it up to where the vacuum actuator was?

patdaly

Bolt it up, but that assumes you don't have any issues with the CAD in the axle.

Tallguy67

Turfguy,
Like Pat said, assuming your CAD engagement sleeve isn't buggered up the work is all done external to the axle housing, wheel on. The only reason I jacked up the passenger side of the truck was to minimize the diff/axle oil that came out of the hole when I took the old CAD actuator off.

I will try to draw the picture with words, if I am speaking down to you please do not take offense.

The way our 4wd system is made, when stock, when you pull the lever to 4wd in the cab, first of all the synchro-mesh in the transfer case gets the stuff in the t-case up to speed and then engages the chain in the t-case to apply power to the front drive shaft. Once the front drive shaft is moving, vaccum is applied to the CAD actuator which slide a sleeve that lives on the inward side of the front, passenger side axle outward to engage a stub-axle a few inches long that connect to the passenger side front wheel. The center part of the axle and the outer axle stub have matching splines and the sleeve has the opposite splines. with the collar slid outward and engaging the inner part of the axle and the axle stub, your passenger side front axle is now solid and power gets applied to the front wheels through the open front diff. All the Posi-Lok CAD actuator does is take the vacuum powered actuator out of the equation and replace by a manually articulated one.
To install, you remove the vacuum actuated CAD, clean up the gasket surface on the axle housing and install a manual actuator where the vacuum one was. The connection between actuator and the CAD itself is a fork (like a tuning fork) that fits into a notch in the CAD.

The hardest part of the Posi-Lok install was drilling the hole through the firewall for the cable and then routing the cable around the engine. Heck, you even get a template that you place around the accelerator pedal mount to show you where to drill the hole. You mount the cable pull under the ashtray.

Let me know if I can answer any more questions. BTW - someone asked me a year or two back if I worked for Posi-Lok or something. The answer is no, I do not but I am really impressed with the high quality and simple product that they build to replace a complicated and unreliable system that Dodge built.

Ok, one last thing I just noticed when reviewing my post, you still have to lock and unlock the t-case as you normally would for 4wd and 2wd, Posi-Lok only deals with the actual CAD.

turfguy

lol No offense taken; I know how it works & did the work replacing the old actusator & got a peek inside when I had it off.
Pretty sure the bushing is buggered too; thats what the mechanic told me. It doesn't line up when I pull the T case lever back.

F. Flack

I found mine was out when I needed to pull my camper out of an off-road area last November after it had rained for over 12 hours. I still have mud stuck on the front of the camper. When I got home (on a dry floor) I found my vacuum line was broke in two places, but was able to splice it together well enough to get me through a couple snowstorms. I had been wanting a reason to buy a posi-lock, so I ordered it and installed it yesterday. So far, all my testing/playing in the snow has been flawless. Using the template, I ended up drilling through the firewall and hit the edge of the backing plate right at the curled edge. It took a little more effort to get the edges smoothed out so it didn't snag the cable. The instructions also indicated to cut a 1" hole in the insulation to drill through -- drilling was easy, but it is nearly impossible to install the grommet with that sized opening. Fought it far too long before cutting more away. I also spent too much time trying to find the best route for the cable so it wasn't too long or short. Finally routed it down and under the frame where the driver's-side brake line runs, then up and over the differential making sure it was clear from the moving parts and rubber "stops".