4WD STILL not engaging correctly GRRRRR

Okay instead of doing the cable actuator thing I figure what the hell I'll rig it up to where the fork slides the collar over permanently, I know someone suggested this. So I fixed it where the fork stayed over to the engagement side all the time, (can't disengage) and left the vacuum lines on there to give it a bit of assistance (constant vacuum pressure in 4WD). So I test drove it (part-time light being on constantly only slightly annoying), I started going around a corner and started hearing a horrible grinding noise and my part-time light started flickering (it was still trying to disengage even though there was no way it could be forced too!) I pulled it up in 4WD and it went away ( I assume vacuum pulled the fork/collar over even further since it can only go that way)

Then I tried making a "T" with the vacuum hoses so no matter if I was in 4WD or 2WD the vacuum would still be pushing it towards the engage side(constant vacuum pressure to engage). It seemed to work okay but when I went from 4WD back to 2WD it started grinding again and trying to disengage (light flickering again even with constant vacuum to the engagement side), I figure it's the collar grinding on the axle shaft? So what does this mean that my collar is totally fried and has to be replaced?? This like just happened, all of a sudden one day the 4WD would not engage. I checked on a new vacuum thing for the axle and the stealership said $250.00! The fork is all the way over and it still does not stay engaged so the cable thing would not have worked anyway.

I'm out of ideas.

A little more info is needed. Did you try moving the collar over manually (removing the cover, sliding it over, replacing the cover) and NOT connecting the vacuum lines? Seems a next logical step in your diagnosis of the problem. I don't understand, if you want it to stay engaged all the time, why you'd bother to hook the vacuum lines back up. There isn't anything inside the disconnect to malfunction, other than the vacuum motor not working. The fork attached to the vacuum motor slides a collar over the splines on the end of both axles, and if it's engaged it will work. You said it works in 4WD, but the light flickers and it starts grinding when you put it in 2WD. This would lead me to believe it's a vacuum problem, and disconnecting the lines should take care of it, once you've moved the collar to the engaged position.

Good luck,

Goatman said:

A little more info is needed. Did you try moving the collar over manually (removing the cover, sliding it over, replacing the cover) and NOT connecting the vacuum lines? Seems a next logical step in your diagnosis of the problem. I don't understand, if you want it to stay engaged all the time, why you'd bother to hook the vacuum lines back up. There isn't anything inside the disconnect to malfunction, other than the vacuum motor not working. The fork attached to the vacuum motor slides a collar over the splines on the end of both axles, and if it's engaged it will work. You said it works in 4WD, but the light flickers and it starts grinding when you put it in 2WD. This would lead me to believe it's a vacuum problem, and disconnecting the lines should take care of it, once you've moved the collar to the engaged position.

Good luck,

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Yes, I took the whole unit off and moved the collar all the way to the engaged side, then put the cover back on. The thing is, with the fork all the way over, it does NOT push the collar over as far as it will go, it kinda sits in the middle of both shaft ends. The fork is over as far as it can possibly go inside the tube.

I rigged up a bolt and washer inside the unit to keep the fork permanently on the engagement side, but in 2WD (part time light on) it will start to grind and the light will flicker like it is trying to disengage even though it can't. In 4WD it works just fine. I just don't understand it, the only thing I can think of is that the teeth on the collar is wore out. I put it back like it was so I could drive home without tearing anything up.

TB-XJ said:

Yes, I took the whole unit off and moved the collar all the way to the engaged side, then put the cover back on. The thing is, with the fork all the way over, it does NOT push the collar over as far as it will go, it kinda sits in the middle of both shaft ends. The fork is over as far as it can possibly go inside the tube.

I rigged up a bolt and washer inside the unit to keep the fork permanently on the engagement side, but in 2WD (part time light on) it will start to grind and the light will flicker like it is trying to disengage even though it can't. In 4WD it works just fine. I just don't understand it, the only thing I can think of is that the teeth on the collar is wore out. I put it back like it was so I could drive home without tearing anything up.

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Sorry, bro', but can you hear what you're saying? The collar HAS to be in the middle of the two shafts so they are coupled together, which is why the fork stops there. If it works right in the 4WD position, but changes when you put it in 2WD, YOU HAVE A VACUUM PROBLEM. Disconnect the lines and see what it does. :doh:

If the fork is locked in place why would vacuum be a variable? The fork is all the way as far as the keepers on the vacuum shaft allows it towards the drivers side of the axle, yet the collar is not engaging both axles even though the fork is all the way over as far as it will go. Vacuum has nothing to do with it cause the fork is now in a fixed position (it doesn't move towards the disengagement side at all, it is fixed to the engagement side permanently but if I shift to 2 wheel drive something is grinding like the collar is slipping.)

Ok, you've got to answer a couple of questions......and please don't keep saying the same thing over and over again.

Does 4WD work? Does it make any noise when the t-case shift lever is in 4WD position?

If 4WD works the splines are engaging correctly with the slide collar and axles.

When you shift the t-case shift lever into 2WD, is this when it makes the noise? Are you sure it's in the axle housing/disconnect and not in the t-case?

Have you driven it with the vacuum lines disconnected? The only thing that happens between the t-case and disconnect mechanism when you shift the t-case lever into 2wd or 4wd is vacuum to actuate the motor. IF it works fine in 4WD, and ONLY makes noise in the disconnect housing when you've shifted into 2WD, the only difference is vacuum which may be actuating the motor slightly, moving it just enough to barely disengage the coupling collar, but not enough to totally disengage because you have the shift fork bolted down.

Pull the vacuum lines off with the collar engaged and see what happens.......it won't hurt you to try.

I pulled it up in 4WD and it went away

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As I said, in 4 wheel drive it goes away, and works fine, I used a T in the vacuum line ONLY connected to the engage side so I would have constant vacuum there, it still did the same exact thing. So the collar shouldn't be moving towards the disengage side.

Sorry if I seem to repeat myself, but it's not exactly easy to explain.

The noise is in the front axle NOT in the transfer case, and it's coming from the passenger side. It sounds like it's right there where the collar engages both axles.

I'm in the middle of building a cable setup for mine right now........do what Richard suggests and loose the vacuum completely and see what the outcome is!

Do you understand completely how the vac circuit from the T-case mounted Vac switch operates? What you're describing is not possible if the vac lines are connected properly, or if the vac is in the constantly "ON" position to keep the shift fork engaged for 4wd mode.

Based on your modification to the shift motor, are you sure that the axle shaft collar is fully manually engaged, don't rely on the vac operated Part Time light.

Could the axle coupling collar be moved too far to the engaged side( left) and not in the middle of the two axleshafts, but then slightly engage the splines when shifting into 2wd, creating the grinding scenario? Bizarro? Yes!

Just trying to help here, keep us updated on the outcome.

TB-XJ said:

As I said, in 4 wheel drive it goes away, and works fine, I used a T in the vacuum line ONLY connected to the engage side so I would have constant vacuum there, it still did the same exact thing. So the collar shouldn't be moving towards the disengage side.

Sorry if I seem to repeat myself, but it's not exactly easy to explain.

The noise is in the front axle NOT in the transfer case, and it's coming from the passenger side. It sounds like it's right there where the collar engages both axles.

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Pull the vacuum lines and tell us what it does......otherwise I have nothing else to say.