Blaine Posted December 22, 2013 Share Posted December 22, 2013 i have a 87 jeep Comanche, converted it to 4wd 2 years ago and just now finally got it running, it needed a transfer case, as well as the vacuum switch on it. the 4 color coded lines that went to the switch were melted so i spliced them with rubber hose. once completed i still didn't have 4wd. noticed the the vacuum lines up under the hood were connected wrong, once fixed, the light inside the cab turned on and 4wd worked. it engaged weather stopped or going down the road and it went in almost instantly. recently though it hasn't been going in as well it takes a few minutes to engage while going down the road and sometimes i have to stop and go through the gears before it will go in, yet the light was on as soon as the lever goes up. so what would be the cause of a slow engaging 4wd? another thing when going down the road in snow conditions between 37-50 when i give it gas the vehicle shakes and when i let off it goes away. doesnt happen in 2wd. Link to comment Share on other sites More sharing options...
Eagle Posted December 22, 2013 Share Posted December 22, 2013 1. Vacuum leak. 2. If there's a vacuum leak, the axle shift motor may not be fully engaging, and under power the connector collar may be slipping. 3. Please don't use funky colors behind your text. It's dang near impossible to read. Link to comment Share on other sites More sharing options...
Blaine Posted December 22, 2013 Author Share Posted December 22, 2013 thanks allot sorry about the funky color i copied and pasted it from another thing i put it on. and i didnt know how to remove it. Link to comment Share on other sites More sharing options...
Blaine Posted December 22, 2013 Author Share Posted December 22, 2013 i edited the orginal question maybe this might help i was a little more specific and i took away the funky colors Link to comment Share on other sites More sharing options...
cruiser54 Posted December 22, 2013 Share Posted December 22, 2013 Here's an excellent solution to your problem and will future issues when you're depending on your 4wd to work. You don't need a light as your shift lever indicates transfer case position. http://comancheclub.com/topic/17377-cad-fix-1/ Link to comment Share on other sites More sharing options...
Blaine Posted December 22, 2013 Author Share Posted December 22, 2013 thank you Link to comment Share on other sites More sharing options...
Blaine Posted December 22, 2013 Author Share Posted December 22, 2013 alright i read through there comments got alot of answers thank you allot, but i have just a few more questions. one i do believe that will worsen my gas mileage because now your pushing drive shaft and transfer case, and two if i leave the vacuum lines hooked up at the transfer case and plug the ones that go to the axle will the vacuum light in the cab still come on, the light is something i gloat a little cuz my dad had many comanches and his light never came on, so once it did i was shocked and a little proud, were both comanche mechanics, have to be to maintain them Link to comment Share on other sites More sharing options...
cruiser54 Posted December 22, 2013 Share Posted December 22, 2013 alright i read through there comments got alot of answers thank you allot, but i have just a few more questions. one i do believe that will worsen my gas mileage because now your pushing drive shaft and transfer case, and two if i leave the vacuum lines hooked up at the transfer case and plug the ones that go to the axle will the vacuum light in the cab still come on, the light is something i gloat a little cuz my dad had many comanches and his light never came on, so once it did i was shocked and a little proud, were both comanche mechanics, have to be to maintain them The CAD was such a worthless, unreliable and costly system that they ditched it mid 91. There is no measurable loss in MPG. Link to comment Share on other sites More sharing options...
Blaine Posted December 22, 2013 Author Share Posted December 22, 2013 and the what about the light in the cab, if i had plugged the lines alright i read through there comments got alot of answers thank you allot, but i have just a few more questions. one i do believe that will worsen my gas mileage because now your pushing drive shaft and transfer case, and two if i leave the vacuum lines hooked up at the transfer case and plug the ones that go to the axle will the vacuum light in the cab still come on, the light is something i gloat a little cuz my dad had many comanches and his light never came on, so once it did i was shocked and a little proud, were both comanche mechanics, have to be to maintain them Link to comment Share on other sites More sharing options...
cruiser54 Posted December 22, 2013 Share Posted December 22, 2013 I've got a vac diagram. Let me look at it. If you have vacuum running to the transfer case switch (red), and the (yellow) line running from the transfer case switch to the light actuating switch below the coolant bottle, along with the black or blue vent line with valve left alone, and eliminating the green line from the transfer case to the front axle. I'd plug it. Might work., Link to comment Share on other sites More sharing options...
Blaine Posted December 22, 2013 Author Share Posted December 22, 2013 cool thanks really appreciate the help, ive tried looking up answer's on google and its hard to get the exact thing you need, so glad i joined this club, Link to comment Share on other sites More sharing options...
Blaine Posted December 22, 2013 Author Share Posted December 22, 2013 and I'm sure I'm going to have to buy i new gasket for the CAD right? do they rip when u pull it off Link to comment Share on other sites More sharing options...
cruiser54 Posted December 22, 2013 Share Posted December 22, 2013 and I'm sure I'm going to have to buy i new gasket for the CAD right? do they rip when u pull it off Nah. I just put a bit of RTV on each side of the old gasket. Link to comment Share on other sites More sharing options...
Blaine Posted December 22, 2013 Author Share Posted December 22, 2013 thanks again Link to comment Share on other sites More sharing options...
Blaine Posted December 22, 2013 Author Share Posted December 22, 2013 alright i took the CAD off the fluid was sludge so I'm cleaning that, now my CAD is all pneumatic it needs air either to engage to disengage so nothing keeps it in the lock or unlock position i can move it with my hand either way easily, the diaphram has allot of grime in the ports were the lines connect could that cause it not to move Link to comment Share on other sites More sharing options...
Eagle Posted December 22, 2013 Share Posted December 22, 2013 alright i read through there comments got alot of answers thank you allot, but i have just a few more questions. one i do believe that will worsen my gas mileage because now your pushing drive shaft and transfer case, Jeep stopped using the front axle disconnect around 1992 or 1993, so ALL XJs from then up to the last one built in 2001 didn't have it -- and XJs with the Selec-Trac transfer case didn't have it. In theory, yes, it probably costs a bit in fuel economy. But you're not driving a sleek, aerodynamic SST, you're driving a brick on wheels. In the real world, you'll never notice the difference. Link to comment Share on other sites More sharing options...
Blaine Posted December 22, 2013 Author Share Posted December 22, 2013 ok seeing the CAD was disconnected i hooked it up to the vacuum lines so i could see if it would move and it does, i had a friend put it in 4 and i saw that the fork moved, but when he disengaged it it didnt come back, which is opposite of my problem, at first it wouldnt engage. but its the green line the runs into the side of the diaphram, that is what returns the fork, no vacuum to it. Link to comment Share on other sites More sharing options...
cruiser54 Posted December 22, 2013 Share Posted December 22, 2013 Lock it in using the write-up from Pete M. Link to comment Share on other sites More sharing options...
cruiser54 Posted December 22, 2013 Share Posted December 22, 2013 alright i read through there comments got alot of answers thank you allot, but i have just a few more questions. one i do believe that will worsen my gas mileage because now your pushing drive shaft and transfer case, Jeep stopped using the front axle disconnect around 1992 or 1993, so ALL XJs from then up to the last one built in 2001 didn't have it -- and XJs with the Selec-Trac transfer case didn't have it. In theory, yes, it probably costs a bit in fuel economy. But you're not driving a sleek, aerodynamic SST, you're driving a brick on wheels. In the real world, you'll never notice the difference. True^^ story. Link to comment Share on other sites More sharing options...
Blaine Posted December 22, 2013 Author Share Posted December 22, 2013 well i fixed it i cleaned out the sludge and put a little gear oil in it. but i think were there was grime in the air ports on the diaphragm and the green line was totally plugged with dirt caused it. i cleaned them and tested it, the fork went back and forth, so i put it back together and it works fine now, it instantly goes in. say in the future if i decide to flip the CAD, what will keep the fork from sliding back to unlock, cause the fork free floats Link to comment Share on other sites More sharing options...
Blaine Posted December 23, 2013 Author Share Posted December 23, 2013 well i fixed it i cleaned out the sludge and put a little gear oil in it. but i think were there was grime in the air ports on the diaphragm and the green line was totally plugged with dirt caused it. i cleaned them and tested it, the fork went back and forth, so i put it back together and it works fine now, it instantly goes in. say in the future if i decide to flip the CAD, what will keep the fork from sliding back to unlock, cause the fork free floats Link to comment Share on other sites More sharing options...
48MJ Posted December 25, 2013 Share Posted December 25, 2013 If it is offset it can't move back that far. Also I've used a hose clamp on the outer axle to hold the disconnect sleeve over. I did mine because when it would freeze it would not ingauge. You won't even notice you did it except you'll always be able to get 4x4. Wait till your in the mud and it pulls your vacume lines off, you'll be glad you eliminated them. Link to comment Share on other sites More sharing options...
Blaine Posted December 25, 2013 Author Share Posted December 25, 2013 well i figured out if you if you keep the CAD in 2wd position, take the c-clip off the rod that holds fork in place and slide the fork to engaged without moving the bar and put the clip back in the original spot, it will hold the fork in 4x4 position, no hose clamp needed. Link to comment Share on other sites More sharing options...
cruiser54 Posted December 25, 2013 Share Posted December 25, 2013 well i figured out if you if you keep the CAD in 2wd position, take the c-clip off the rod that holds fork in place and slide the fork to engaged without moving the bar and put the clip back in the original spot, it will hold the fork in 4x4 position, no hose clamp needed. Exactly. Simple.... Link to comment Share on other sites More sharing options...
Blaine Posted December 30, 2013 Author Share Posted December 30, 2013 Ok looked over the front driveshaft and you were right cruiser, one of Ujoints were bad, another thing though is there is play in the yoke on the front diff, with oil slowly coming out, so the seal needs replacing but will that fix the play, and is there a crush collar as well? this is not mine this is a ref. picture, basically the yoke can move up and down Link to comment Share on other sites More sharing options...
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