Command trac vacuum system

[JVRacer04]

Im converting my 2wd to 4wd... i have a aw4 w/ np231 and the 2piece front axle with vacuum disconnect...

i was wondering where the stock mounting location is for the Indicator switch?

here is the diagram:
http://xjconnection.jtv.cc/fiches_X..._vacuum_hoses__XJ_1987_1991__t_case_AM231.JPG

Vaccum Indicator switch:
http://cgi.ebay.com/ebaymotors/ws/e...&item=7931669092&rd=1&sspagename=STRK:MEWN:IT

can anyone out there lend me some tips for the vacuum sys in general.. that diagram isnt quite in simple wording

thanks!

 

[Matthew Currie]

The vacuum switch that controls the axle is mounted on the transfer case, as I'm sure you've figured out. I don't remember the color coding, but there will be four lines attached to that. One is the vacuum source, which goes to the vacuum reservoir. One is "engage" and one is "disengage" and the last one is the vent, which dead-ends at a filter, usually found hanging from the vacuum harness on the passenger side of the firewall next to the engine. As originally set up, there would be a big rubber four-hole plug at the end of the harness of plastic tubing, that simply presses onto that switch.

On the axle vacuum motor are three nipples. The one furthest inboard is for "engage," the one outboard is for "disengage" and the one between, nearer the engage side, is the one which actuates the indicator light switch. This is a vacuum operated switch which traditionally lives on the right inner fender. The 4WD indicator on the dash, in other words, is lit when the axle successfully connects, rather than when the transfer case is shifted.

The standard setup includes sections of plastic tubing and a couple of sections of metal tubing, all fairly carefully routed, and terminates in a multi-holed rubber connector at the vacuum motor, but it should be possible to do the whole thing with a large amount of tubing alone, if you can't get all the factory bits. If possible, I'd try to use metal tubing for at least part of the setup, to help keep it from being vulnerable to trail debris and the like.

 

[tchase]

The vacuum switch that controls the axle is mounted on the transfer case, as I'm sure you've figured out. I don't remember the color coding, but there will be four lines attached to that. One is the vacuum source, which goes to the vacuum reservoir. One is "engage" and one is "disengage" and the last one is the vent, which dead-ends at a filter, usually found hanging from the vacuum harness on the passenger side of the firewall next to the engine. As originally set up, there would be a big rubber four-hole plug at the end of the harness of plastic tubing, that simply presses onto that switch.

On the axle vacuum motor are three nipples. The one furthest inboard is for "engage," the one outboard is for "disengage" and the one between, nearer the engage side, is the one which actuates the indicator light switch. This is a vacuum operated switch which traditionally lives on the right inner fender. The 4WD indicator on the dash, in other words, is lit when the axle successfully connects, rather than when the transfer case is shifted.

The standard setup includes sections of plastic tubing and a couple of sections of metal tubing, all fairly carefully routed, and terminates in a multi-holed rubber connector at the vacuum motor, but it should be possible to do the whole thing with a large amount of tubing alone, if you can't get all the factory bits. If possible, I'd try to use metal tubing for at least part of the setup, to help keep it from being vulnerable to trail debris and the like.

That pretty much covers it. I can add one thing though, depending on the year of your donor axle, your axle vacumn motor may only have the two engage/dis-engage lines. This type used on later models (not sure of the years but my '91 had it), used an electrical switch on the axle motor to activate the light. Other than that I think the two systems are pretty much the same.