RLCollins Posted December 7, 2009 Share Posted December 7, 2009 I need a Schematic or guidence to find where a lost vacuum line is suppose to be landed for the four wheel drive (transfercase) operation. After removing to coolant pressure bottle from the old cooling system along with cleaning up the wiring and vacuum lines. I have a lost end, it is the blue vacuum line going to ???????????. The yellow, green and red have places to go, but not the blue. :help: 1989 MJ long bed with 4.0 MPI I-6 Link to comment Share on other sites More sharing options...
JeepcoMJ Posted December 7, 2009 Share Posted December 7, 2009 I need a Schematic or guidence to find where a lost vacuum line is suppose to be landed for the four wheel drive (transfercase) operation. After removing to coolant pressure bottle from the old cooling system along with cleaning up the wiring and vacuum lines. I have a lost end, it is the blue vacuum line going to ???????????. The yellow, green and red have places to go, but not the blue. :help: 1989 MJ long bed with 4.0 MPI I-6 IIRC, blue is just the vent line for when the disco slides over. Link to comment Share on other sites More sharing options...
jpdocdave Posted December 7, 2009 Share Posted December 7, 2009 http://www.wranglerforum.com/showpost.p ... ostcount=6 Link to comment Share on other sites More sharing options...
Pete M Posted December 7, 2009 Share Posted December 7, 2009 the transfercase is manually actuated by the big lever in the cab. those vacuum lines come from a little switch on the t-case and go to the CAD (central axle disconnect) on the front axle. The CAD is vacuum actuated. I suggest ripping out all those problematic vacuum lines, plugging the source, and shifting the CAD so that it is engaged all the time. This will not affect any of the 4wd functionality of your truck (Jeep did away with that stupid CAD in the early/mid 90s), it'll only make it infinitely more reliable. :thumbsup: See here for steps to defeat the CAD once and for all: viewtopic.php?f=9&t=18415 Link to comment Share on other sites More sharing options...
RLCollins Posted December 7, 2009 Author Share Posted December 7, 2009 yep - In theory you disengage the front axle through the vacuum shift motor. Does this improve gas milage, since you would not be turning everything in the drive line? or is this just in theory? I guess it is an expensive way to turn on the dash light letting you know that it is four wheel drive. What has been your experience with this system Yes I agree If it only turns on the dash light, than JUNK it. What would you replace the front end with? I thinking along the lines of something with manual hubs? or I'am I thinking in a wrong direction? :dunno: Link to comment Share on other sites More sharing options...
JeepcoMJ Posted December 7, 2009 Share Posted December 7, 2009 yep - In theory you disengage the front axle through the vacuum shift motor. Does this improve gas milage, since you would not be turning everything in the drive line? or is this just in theory? I guess it is an expensive way to turn on the dash light letting you know that it is four wheel drive. What has been your experience with this systemYes I agree If it only turns on the dash light, than JUNK it. What would you replace the front end with? I thinking along the lines of something with manual hubs? or I'am I thinking in a wrong direction? :dunno: it worked in theory, but had negligible differences in them. Link to comment Share on other sites More sharing options...
Pete M Posted December 7, 2009 Share Posted December 7, 2009 just follow the instructions in that link and your front end will act like any other Jeep front end since they dumped the system for good. :thumbsup: No need to swap axles just because of the CAD. the only potential downside is if you've got a bad joint in the front driveshaft. That can cause vibrations. But if you've got a bad joint, you really should fix it anyway so finding out can be a good thing. :D If it really truly made a positive mpg difference, wouldn't ya think Jeep would still be doing it? With all the modern CAFE requirements, I would think they'd be looking for any and all real gains. Link to comment Share on other sites More sharing options...
RLCollins Posted December 8, 2009 Author Share Posted December 8, 2009 When I talk about changing the front axle, it is for strength purposes. Down the road I will change both the front Dana 30 and the rear Dana 35. I will also junk the Pewgoat BA10-5. I have a NP 231 transfercase. What would you change to turn this truck into a MUD HOG, ROCK climber? I live in South Florida where the weather is hot and the mud is DEEP. :chillin: Pete when jeep removed the CAD system in the mind 90's what did they use in its place? I bleieve in the KISS method, Keep it simple stupid. So I want to strip everything that is not needed. Throw the anchor overboard so to speak. The only power I want left is the radio AC. There are no power windows, seats, minors or anything like that I just want the truck to run and be street legal. I don't want to cut it up, but keep it as close to original as possible. But with the strength in the drive train to go just about anywhere. :thumbsup: Link to comment Share on other sites More sharing options...
Pete M Posted December 8, 2009 Share Posted December 8, 2009 what size tire? The Dana 30 can be built to handle a decent load and you can mate it to a 44 or Explorer 8.8 in the rear. If you're prepared to take on a big project, my standard suggestion is to look into late 70s Ford 3/4 ton axles. The front axle will be a heavy duty 44 with a drivers side diff, and it will readily accept the MJ suspension brackets (get aftermarket though, it'll be much stronger than stock). you don't necessarily need the rear from the same truck though, as just about any 8 lug dana 60 from any truck will match up in width. Link to comment Share on other sites More sharing options...
Pete M Posted December 8, 2009 Share Posted December 8, 2009 I split your questions off into a new thread. :thumbsup: Link to comment Share on other sites More sharing options...
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