mppd20

Just bought a 94 CTD with NV4500 and NP231HD, I went to use the 4x4 this morning, to no avail. I got a lot of grinding and occassionally was able to lock it in. I changed the vacuum actuator on the front rear and it would lock in everytime. Here is my problem now, it does not stay locked in, it is kicking out, the light goes out for an instant or flickers and you can here and feel it locking and unlocking and it does not sound good. Would this likely be a vacuum leak, or is the switch on the case going bad. I can feel vacuum on one line to the vacuum solenoid, but only slight on the other, should they both have equal vacuum? Thanks!!

boughtadodge

I had one come in the shop last week with the same problem. It had a vaccum leak that was causeing the problem but the owner had let it go so long that it wore the fork on the front axle disconnect so I had to replace it. Check the fork on the front axle there is four bolts on the vacuum pod and then just remove it check it closely for wear and check for vacuum leaks.

torquefan

Check vacuum to the actuator with a gauge. Should have vacuum on one line in 4wd and the other line in 2wd. Vacuum should be over 12" . Remove the disconnect cover, check the fork. It should slide both directions without binding, and have no obvious bends or sideways slop. Inspect the 2 shafts that meet in the disconnect housing, they should meet each other squarely, and should have almost no radial movement against each other. The splines on these shafts should have nice square edges, and not worn on an angle. The sliding collar should slide back and forth on the shafts without binding, as long as the splines are aligned with each other.
Back to the fork, I almost forgot: on each tip of the fork, there should be a plastic pad where it rides on the sliding collar. If the pads are gone, it won't stay engaged in 4wd.
Hope this helps.

mppd20

I did replace the entire assembly on the front housing, on the old one, the vacuum part spun freely so I assumed it was the problem. That solved the slow manner that it locked the front in, but when I drive it, it is hopping in and out of 4x4. Where is the line that comes from the engine compartment to the case switch running? I am getting vacuum to the front solenoid but I dont know how much, could it not be holding enough vacuum and it is losing it, unlocking, and going back in again? Everything looked good when I had the fork pulled out as far as gears. There was a little spring that was long but really small that came out, I belive it was from the old solenoid as it was binding up constantly. When I put the new fork and solenoid in, I would pull the lever, and it would sometimes take up to 15 seconds to lock the front, sometimes longer??

Crimedog

If you are getting partial vacuum in one line and full in the other, then the switch is probably bad. It isn't bad at all to replace. I did the switch and complete set of 4wd vacuum lines for less than $65 if I remember.

Big Smoky

I bought a manual pull cable to eliminate the vacuum system. A company called posi loc makes it and it is a whole different pod that bolts right up. Do yall know if you are suppose to be able to move the axle up and down and side to side inside the housing? I think that is one of my problems too. Does anyone know how to fix it?

TxDiesel007

Hmm..

im not too fond of the dodge 4x4 system myself, it was takin forever to engage, i did switch out the vaccum lines myself for about 58 dollars with the help of my father, seemed to solve my problem well, ive looked into the posi lock kit.. I might get it eventually........

matador

How tough are those posi locks to put on and how expensive are they?

Crimedog

I also looked into the Posi-Lok system, there are a few reasons I got turned off of the system, one is from another member when we were discussing it. If you look at the Posi-Lok website they seem to imply that the last little bit is hard to engage, this does not seem very strong to me if it is only partially engaging it. Also, up here in the snow and salt (if we ever get any this winter ) it wouldn't make sense to have a cable running down being still for a few weeks or maybe a few months at a time, and then when you need it the cable gets seized up. The vacuum system is a sealed system that works fine when it is properly maintained. I spread silicone around the connections and zip tied them to ensure no moisture gets in them.