There is an image of the Posilock system,

This post below is just FYI and just some reading for you incase you are interested more in the posi lock system. I highly recommend it, no more doubts if the 4wd engages or not...

https://www.dieseltruckresource.com/...ad.php?t=73706



Rick

 

Well I took the truck out for a test drive just now and if I very gently accelerated and shifted through the gears there was no noise but if I accelerated in a regular manner, but not tromping on it , the noise would appear. All this in 2wd. I put it in 4wd and drove home and couldn't get it to make a sound! Does that still seem like it is the CAD? I don't have any test equipment so how do I check vacuum on the CAD and if I don't go the Posilok route what am I looking at for cost to fix or replace the CAD?

 

Simple procedure to check vaccum

i think u can buy a vaccum gauge and see what it does, But what i did was first of all make sure that all of the vac lines were intact and zip tied, with the truck running i pulled the little connector to the vac actuator and one of them had vaccum pulling back on the collar in 2wd, the inverse when u put it in 4wd, the other line just blows air to move the collar across and engage the 4wd..

The CAD, i think can be replaced for about 75-80 dollars or so, but i think its best to posilock it and forget it, id never go back to a CAD and have doubts if the system works or not. Remember, just one disconnected line and ur 4wd might not even work, so why risk it?

Rick

 

TXDiesel007,
I pulled the vac lines from the actuator and fired up the truck. In 4wd I got suction on the black line and nothing on the red. In 2wd I got suction on the red line and nada on the black. Does that sound right? Is there any way to test the actuator? Like I said earlier ,the fork does move when engaging the tcase. Is it possible that while it is solid in 4wd, when put into 2wd it somehow slips and tries to engage 4wd?

 

I had a strange noise once...thought it was bearings in tranny. It would grind under normal acceleration but not very light acceleration. Turns out the snap ring on the t-case output shaft had shattered. I don't think this is your noise but I thought I'd share.

 

That is exactly how the stock system is supposed to work...

However, im sorry to say im not too sure about the second one, but id take a guess that it shouldnt move... it only makes sence if the vaccum is doin its work...

Rick

 

You know the more I cipher on this and get info and ideas from folks, the more it seems it isn't the CAD. The noise really sounds like it is coming from the tcase/trans area. It only happens in 2wd ,never in 4wd. If it was something in the trans it should happen all the time. If in the tcase it is possible to only happen in 2wd. The tcase was "rebuilt" by the Ist owner and I have to talk to him about that to see what he may know.

 

Did we ever find anything out on this one? I am having the EXACT same problem, it sounds like it is coming from the CAD assembly and I have removed everything, replaced a bent vaccum shaft rod and it is still there.

Did the OP ever find the problem? Was it the snap ring on the t-case? Can you get to this snap ring with the t-case still in the vehicle?

 

I don't think it is the snap ring but to answer your question, no, you do not have to take the t-case off to replace this particular snap ring. The ring lies behind the bearing that is in the tailshaft housing that houses the vss. Just drop your sriveshaft and take off the first tailshaft housing, just 4 bolts IIRC. You will then see the bearing and snap ring I am referring to. I did however drop my t-case because I didn't know what was wrong with it. To replace the snap ring I didn't have to drop it but to get the pieces out of the t-case I did have to drop it and split it. Fruitcakes, maybe you need to check the shifter linkage as it may be inproperly adjusted keeping the shift collar riding on the syncro or the edge of the gear?? If I had eliminated everything but the t-case I would just drop it and take a look at it and see if there is anything in it wrong. If you are descent with a wrench I'd say go for it, not much to a t-case but bearings, shafts, and one big chain. Just make sure you remember how it goes back together! Oh yeah and some permatex helps too.

 

The original rebuild of the tcase was done because the big snapring on the mainshaft came off and things spread and started grinding. It was noisy both in 2wd and 4wd. I called a trans shop and he said it sounded like a bent fork or maybe snapring. Now that I think back on the whole evolution of the problem, it seems I may be the culprit. When I first got the truck , I tried to put the tcase into 4lo and had a little difficulty, no forcing or grinding but it was balky as I am not used to the action after years of my GMC trans. Is it possible I bent a fork in the tcase trying to find 4 lo?. I did get it to engage, but the next morning I put it back into 2 wd and drove off at which point it began to make the noise.

 

Mine just started to do this, and I did a search and found your post. I've ripped the whole front end apart because thats where it sounded like it was coming from and I could not find anything to indicate that it was anything in the front end.

This afternoon I pulled the tailshaft housing (about a whole 10 minute job or so) and sure thing, there was piece of snap rings in the tail shaft housing. I had to order a new snap ring so I am not sure if the problem is 100% fixed or not yet. I will update as soon as I find out tomorrow.

 

Took the truck to the trans shop at 9 am today and it was fixed by 11:30. A snapring had broken in the transfer case. He replaced it with a Ford snapring claiming they were a better quality unit! I am a happy man. Tomorrow I pick up the truck and head over to talk to some local diesel truck service guys who run Dodge Cummins. Getting local expertise is a bonus.

 

Well I didn't think it would be your problem but hey, $10 fix aint too bad eh? I thought mine was my tranny bearings finally going out but tore into the t-case and found the bad snap ring. My problem was mine happened to go out Thanksgiving weekend and I had work/class on Monday morning. I finally found one at the local Deere dealership. I just attributed mine to the added stresses of burnouts on 40's .