question about 4X4 vacuum

[jim]

In the 83 wagon the dash switch will not activate the 4X4.    I have locked the front axle so don't need vac to it.  I want to simplify  the vac system as per Gronk's method.  It shows a single line from the switch to the shift motor.  However, the switch, and also a switch I have from a non-disconnect axle, have 3 ports for vac hoses.   Which one would I connect to, and what do I do with the other 2?

[GRONK]

I'll need to dig through the notes on this one.  Might take a couple of days.

[68AMXGOPAC]

You should be able to either blow through the port ( yes with your mouth and a small length of hose ) or apply vaccumm , and see wich line the switch will pass it through when it's moved left or right...... and I would assume connect it to that one... ?? sounds simple heh. : )

[mick]

You should be able to either blow through the port ( yes with your mouth and a small length of hose ) or apply vaccumm , and see wich line the switch will pass it through when it's moved left or right...... and I would assume connect it to that one... ?? sounds simple heh. : )

Exactly.  You have a supply port, a 2wd port, and a4wd port.  The actuator on the t-case requires vac both directions to hold the selected range.  The blow method works just fine for figuring it out.

[carnuck]

I've done this a number of times on FSJs and I'm about to do it on my Eagle wagon before I put the 727 in (decided to wait till spring for the AW4 conversion so I'll have 4wheel drive this winter)
Vacuum comes from the motor to the vacuum ball first (so you have a reservoir with a check valve) Then it goes to the dash switch through the red line.
   The dash switch has 2 lines out and you need both if you want to be able to switch between 2 and 4 wd. With the front diff locked and out of the equation, you can remove (I almost said rip.  ) those lines so you have only 2 going to the tcase motor.
   Make sure the tcase motor is functional. I take it off and see if it moves back and forth or it's rusted up inside. (if rusted too much, I replace it with one for an '88 to '91 Grand Wagoneer because it only has the 2 ports you need already) Lubricate it AFTER ensuring the diaphragm isn't shot. Use something that won't eat the rubber or you'll be right back in to do this again soon.
Here's the direct link to vacuum diagrams, thanks to Tom "Ol Jeep" Collins
These are for the FSJ, but the system is the same
http://oljeep.com/gw/vac/axle/83-84-FSJ-FrontAxle2-whl.jpg
http://oljeep.com/gw/vac/axle/83-84-FSJ-FrontAxle4-whl.jpg
This is what the parts look like in real life:
http://oljeep.com/gw/vac/axle/83-84-FSJ-FrontAxlePictorial.jpg

Here's the Eagle vacuum axle/tcase diagram for comparison (PDF download only)
http://oljeep.com/gw/vac/eagle/EagVac.pdf

Back to the hook up: In the diagram below
http://oljeep.com/gw/vac/axle/83-84-FSJ-FrontAxle2-whl.jpg
at the bottom right of center is the tcase shift motor.
Without the front axle rubbish, the "front axle connecting port" needs to be blocked off. I use silicone sealer and a vacuum cap with a hose clamp to ensure it stays.

Then the check valve delay isn't needed or the lines to the front axle connecting port.
Everything on the bottom left corner can be removed and the lines reconnected like this:
Green line from dash mounted mode selector vacuum switch to the rear port on the tcase motor (remove the line to the delay valve from the system so you go direct)
Yellow line from the dash mounted mode selector vacuum switch is re-routed directly to the front port of the tcase shift motor.

*NOTE* If your front axle is NOT permanently engaged, shifting into 4x4 without it being locked will result in catastrophic tcase failure if you have a NP119, NP129, NP128 (although that one takes longer), or a swapped in NP219, NP229, NP228 (takes awhile, like the NP128 because it doesn't have a viscous coupler, but excessive revving will blow up the tiny differential in it)
If you have a NP208, it has no viscous coupler but it doesn't play well in good traction areas in 4wd. The suspension winds up, making it hard to steer and actually twists VERY hard on ujoints, etc. On dirt, snow, etc, it's awesome.

[jim]

Thank you very much for all that information.  I'll sort through it when I have more time.
However, my mode switch has 3 ports.
This is the 83, stop to shift but I did lock the front axle with the hose clamp method.

[mick]

You can remove that pull down thingy and have shift on the fly since your front axle is clamped. 

[carnuck]

Thank you very much for all that information.  I'll sort through it when I have more time.
However, my mode switch has 3 ports.
This is the 83, stop to shift but I did lock the front axle with the hose clamp method.

All the diagrams I posted have a 3 port dash switch.

[jim]

Carnuck, I wasn't feeling well last night didn't stay up to research the info.  I hope to be able to do that tonight.  That's good to know about the switch.

I had thought about removing the pull down knob but wasn't sure how to do it.
I have a switch from a non-disconnect Eagle but it's the wrong color.  I may paint it and try to get the resident in-house artest to paint the lettering.

[carnuck]

I'd lock up the front axle first. There is a C clip holding that pin and spring in. Pull the clip and reinstall the switch. Piece of cake!

[jim]

Front axle has been locked in for almost a year.  I'll look at that switch.  It would easier to pull a clip than repaint.

[jim]

I finally got a chance to look over this info somewhat.  I still need to spend more time with it, but I'm beginning to get a pretty good idea about all of it.
I do have a question about this:

"Vacuum comes from the motor to the vacuum ball first (so you have a reservoir with a check valve) Then it goes to the dash switch through the red line."

Would it be feasible to come directly from manifold vacuum to the switch?  I'm concerned about losing something else if I remove a hose from the vac can to connect the switch to it.  I already have a tee with one side plugged at manifold vac.  If you say it is necessary to use the vac can I can probably find a way to tee into it.  I think the yahoo that installed the motor plugged it.

[carnuck]

The vacuum can was stock for the 4x4 system. There should be 2 in your car. One for heater/ac and one for 4x4. Ball shaped usually. Jeeps use a football shaped one behind the front bumper.

[jim]

My heater/ac vac connects to the ball shaped can on the driver side fender.   There is another on the passenger side firewall for cruise and other stuff.  I'm not where I can look at this time but at least one and maybe both Eagles have a vac anc inside the drive side wheel well.  I have seen the vac lines running through the inside fender.

Is it necessary to use the vacuum cannister or is it feasible to run directly from manifold vac to the switch?

[ammachine390]

Is it necessary to use the vacuum cannister or is it feasible to run directly from manifold vac to the switch?

I believe the purpose of the ball is to have a vacuum reserve, for low vacuum conditions. Without the ball, you would lose vacuum to the transfer case vacuum motor, and with no vacuum on either side of the diaphragm, I bet it might be able to go into false neutral. You sure wouldn't want that to happen when merging onto a highway.

I don't think AMC would have put it in there if it wasn't necessary (and they didn't even think a metal valve cover was necessary).