Engine/Transmission (1994 - 1998) No 4WD!

[Got Smoke?]

Well I got into a sticky situation yesterday. I parked on some dirt for about 30-45 minutes and my truck sank in a little. When I went to leave it wasn't happening in 2WD. So I though no sweat pull back the "magical lever"... ... nope! #@$%!



Got out and started checking things. Here's the list so far:



Vacuum lines @ the crossmeber where they plug into hard lines

Big 4 Vaccum line on top of X-fer Case

Vaccum lines at the frame above front axle where they go from hard to rubber again.

Vaccum lines at the CAD unit on the front axle.

Vaccum lines in the engine compartment (Thanks for walking me through that JR, there's too dang many up there)



After all that it still didn't work, and the 'ol "When in doubt... ..... " didn't work either! #@$%! #@$%! #@$%!



I ended up pulling the CAD unit off the front axle and sliding the collar over manually. As soon as I did this and attempted to pull out I heard a loud BANG! I stopped, checked the collar and it appeared to have moved over even more and locked in place. Tried it again and still no 4WD. All this time also the 4WD light on the dash never came on.



HELP!

 

[moparguy]

Man, you've tried all the proper things, at this stage, I'd put it up on jackstands in the shop and see if the front driveshaft has power to it. May be the x-fer case.



Good luck, RJR

 

[JGheen]

Sounds like you have a serious CAD problem, Mark.

Since you checked all the lines real well, have you checked your vacuum pump for proper operation? Are you sure all the vacuum lines didn't have a crack or anything in them?

A nice alternative to the vacuum is the 4x4 Posi-Lok Cable . I installed one on my truck about 6 months ago and couldn't believe I didn't convert it sooner. I was also able to clean up and remove all those vacuum lines all the way up to the engine compartment. Looks much better underneath without all those lines everywhere and no worries of loosing vacuum in the heat of being stuck in 2WD.

Hope your CAD is Ok, I doubt anything is wrong with the transfer case... keep us updated on how things go.



Joe

 

[Got Smoke?]

Came home and put the truck up on stands... ... ...



Front shaft spins, front tires don't! :{

 

[Got Smoke?]

Ok now I've swapped out another CAD from a buddies truck... . no change... . stuck my fingers on the ends of the lines and it doesn't have hardly any vaccum AT ALL! #@$%! Where should I start looking?

 

[JTeague]

Make sure you have good strong vaccuum to the switch on the transfer case first. Then take the 4 way vaccuum switch plug and plug the port with full vaccuum individually to both of the hard metal lines on the crossmember. One should engage the front axle and the other should disengage the front axle. If this is the case, the problem is most likely the switch on the transfercase. Hope this helps.

 

[moparguy]

Went through a similar deal with lit'l bros truck a few days ago. His problem was a pulged port on the vacuum switch (the black female boot had been off for a time and reinstalled). I bought a new one for $19 or so from Dodge. Then a couple of days later while browsing at AutoZone, saw the exact piece on a display for Jeeps for $14.



Good luck, RR

 

[pwknapp]

I've got the same problem. Good suction to the transfer case 4 way plug but no suction to either side of the two lines going to the front axle. Replaced the transfer case vac switch and stil no luck. Geting tired of the wife and neighbor towing me up to the house. Worse still the neighbor is pulling me with an 80 something f150. Can't handle the jokes anymore.

 

[DBraunig]

you should see 15 inches of vacuum at the front axle actuator or more. any less and you got a leak or weak vac pump. check for other leaks in vacuum. supply for a/c housing on right rear engine compartment, cruise servo, etc. if your getting 15 at the front then its a mechanical problem. if the bushing in the intermediate shaft in front axle is gone it won't matter how much vacuum it makes because the intermediate axle will drop lower and the collar will bind. did you notice while you had the actuator off if both those axles are lined up together? does the collar slide back and forth easy with your fingers? hope this helps, Dave.

 

[AMink]

On these trucks, don't we have to be moving forward a little to get it to lock into 4x4? Or does the vacuum make it happen even if we're not moving? I had a Mitsubishi/Dodge that if you couldn't move, you couldn't get it into 4. I still wish we could get locking hubs that didn't cost an arm and a leg! Already have to pay for fuel. $2. 69 in Reno :{

 

[Got Smoke?]

if your getting 15 at the front then its a mechanical problem. if the bushing in the intermediate shaft in front axle is gone it won't matter how much vacuum it makes because the intermediate axle will drop lower and the collar will bind. did you notice while you had the actuator off if both those axles are lined up together? does the collar slide back and forth easy with your fingers? hope this helps, Dave.

I have never dealt with vaccum before so I'm not sure what 15in should feel like, but I'm almost dead positive it wasn't that! :{ I held my fingers over the lines and barely even felt a pull against them.



The axles lined up fine horizontally, but I did have the put the T-case in Neutral and wiggle the front d-shaft while sliding the collar over to engage the axles. I'm almost positive its in the the t-case now, and here is my reasoning.



The front d-shaft spins when you put the t-case in any 4x4 mode, I manually slide the collar over and it was LOCKED in solid (took a lot of wiggling of the front shaft to disengage it), and I have a SEVERE leak coming from the T-case FORWARD from the tailhousing. :{ :{ :{



It will be Saturday before I can pull the T-case to inspect the damage.

 

[I-6DZL]

it's not the T-case... You said you put the range selector into 4wd, and the front driveshaft turns. That right there tells me the T-Case is fine. Unless it's making a terrible noise when locked into 4wd.



You need to go buy a vacuum gun. Get one that can apply and feel vacuum. That's the only way you're going to see if you have proper vacuum at the cad. If you don't then take the vacuum supply line and plug one end and apply 15 in of vacuum at the other end to see if you have a hole in it.



I wouldnt pull the T-Case until you've narrowed it down a little closer. With the above statement i would rule out the T-Case in its entirety. right now anyway.



Good Luck

Curtis

 

[Got Smoke?]

it's not the T-case... You said you put the range selector into 4wd, and the front driveshaft turns. That right there tells me the T-Case is fine. Unless it's making a terrible noise when locked into 4wd.



You need to go buy a vacuum gun. Get one that can apply and feel vacuum. That's the only way you're going to see if you have proper vacuum at the cad. If you don't then take the vacuum supply line and plug one end and apply 15 in of vacuum at the other end to see if you have a hole in it.



I wouldnt pull the T-Case until you've narrowed it down a little closer. With the above statement i would rule out the T-Case in its entirety. right now anyway.



Good Luck

Curtis

On 2005-04-11 07:33, Madd Ramm wrote:

If your front driveshaft is turning via the t-case, then there is nothing wrong with the t-case.

The above added quote is from my 4x4 Website www.PavementSucks.com that does rule out the T-case, and now I'm worried its in the front diff. :{ I will pull the front cover one day this week. :{ :{ :{

 

[moparguy]

Curtis gives good advise. A coupla of thoughts. There are many opportunities for leaking connections and damaged vacuum hose/lines. I'd try these two things before I got too involved in tearing into things.



1. Get a length of vacuum line from Napa or somewhere and go from the engine compartment to the Cad unit with vacuum. If it works, then look for leaks, as I recall, Dodge has a new line kit for around $30 or so.



2. If you have a leak, you can pull the vacuum switch form the transfer case and (after noting the position of the various colored lines), pull the lines from the rubber female boot that pulgs on the vacuum switch, take it and the switch to the bench and silicone the boot to the switch, being careful not to get silicone into any of the ports.



Item 2 is what really got Lit'l Bro back in biz.



Good luck, RJR

 

[Got Smoke?]

Curtis gives good advise. A coupla of thoughts. There are many opportunities for leaking connections and damaged vacuum hose/lines. I'd try these two things before I got too involved in tearing into things.

Good idea's, but I have already MANUALLY slid the collar and the front axle still would not pull. If the front d-shaft is turning when in 4x4 but sliding the collar over manually doesn't fix it not only is it vaccum but its something in the front diff. :{

 

[moparguy]

My bad, you're right. Sounds like it's time to pull the old diff. cover and look at the ring gear and pinion. But, if you had issues there, you'd think it'll be easy to feel or hear. Same with a broke axel.



Good luck, RR

 

[JAmos]

I could be wrong but my understanding of the cad operation is that it needs vacuum to hold the fork and collar in both positions. Basically I'm not sure if the fork and collar will stay engaged if moved manually, explaining the bang/pop you heard after you manually moved the fork.



If someone has the part number for the vacuum switch that replaces the switch on the t-case that is supposed to be available for about $20, could you post it? I have been to a few truck shops, looked at several valves, and haven't found anything that will work.



Jordan

 

[DBraunig]

when you slid the collar over manually, it has to be centered so that it covers both axle splines. at this point you should be able to roll the tire with your hands and watch the shafts turn. if you turn the passenger wheel then the driver wheel should rotate in the opposite direction and at the same time you should see the front driveshaft (to transfer case) rotate also. if you manually lock the collar at the shift motor, and turn the tire, and the other tire does not rotate, you got problem in the front differential. 15 in of vacuum will stick to your finger. Dave

 

[Got Smoke?]

Well I found my problem :{ :{ #@$%! #@$%!



When we reinstalled the head the vaccum line that goes from the T-port up on the cowl to the transfer case switch got pinched under the head.



:{ #@$%!



For right now its patched with some air brake hose I had lying around for my air horn setup, and the 4WD works great now. It will be a while before I can afford to pull the head and install a new gasket. Talked at lenght with JR and he said if it wasn't in the budget right now, its driving fine, and my only syptom is a small oil leak then leave it till its in the budget. So I guess that's what I'm going to do.



Gonna dyno it still on the 6th and pray the gasket and o-rings hold, however if it doesn' then I will have to miss the pull on the 7th while I'm tearing it down since I'm off that Saturday.



Pray for my HG. :{