xjman4 Posted July 12, 2009 Share Posted July 12, 2009 i have a 1987 Comanche and the 4WD doesn't work. i have it up on jack stands and the front drive shaft spins but the front tires don't. any ideas? Link to comment Share on other sites More sharing options...
Geonovast Posted July 12, 2009 Share Posted July 12, 2009 You CAD(Central Axle Disconnect) is not functioning. On the right side, under the UCA, there's a metal plate with a vacuum actuator attached. The vacuum lines run to the T-case, and it engages the front axle when you put it in 4wd. Easiest fix is to simply eliminate that function. Remove the vacuum lines off the actuator and T-case, cap the lines on the case. Remove the housing for the CAD, and shim the fork over so it's always engaged. It's pretty simple how it works, you'll see when you get it off. The CAD only survived for a few years, Jeep had completely done away with it after 93. Link to comment Share on other sites More sharing options...
xjman4 Posted July 12, 2009 Author Share Posted July 12, 2009 thank you so much!!! you guys here at the Comanche club are always so helpful :D Link to comment Share on other sites More sharing options...
BlueXJ Posted July 12, 2009 Share Posted July 12, 2009 Another solution is to replace the two piece axle on the passenger side with a one piece out of a non disconnect Dana 30 axle. Then you won't need the fork and it can be eliminated and a plate welded over the hole in the Dana 30 where the disconnect is currently located. Link to comment Share on other sites More sharing options...
xjman4 Posted July 12, 2009 Author Share Posted July 12, 2009 thats exactly what i want to do!!! I heard there was a kit to do it with that gives the needed seals and block off plate. Link to comment Share on other sites More sharing options...
xjman4 Posted July 12, 2009 Author Share Posted July 12, 2009 but having the jeep in four wheel drive the entire time will ruin the tcase when i drive on dry pavement won't it? also will i be able to have four low? Link to comment Share on other sites More sharing options...
Pete M Posted July 12, 2009 Share Posted July 12, 2009 Eliminating the CAD won't put you into 4wd. That will always be controlled by your t-case shifter. :thumbsup: Link to comment Share on other sites More sharing options...
Automan2164 Posted July 12, 2009 Share Posted July 12, 2009 The CAD was just Jeeps way of eliminating rotating mass in the front, like selectable hubs would. By disco-ing the axle on one side, it stops the inner half of the P/S axle from spinning, and allowed the D/S shaft to just rotate the spider gears and not the whole carrier. Which in turn, would keep the front driveshaft stationary. What is it for? To save rotating mass, and by having less stuff spinning, and slowing the truck, save fuel. Does it work? Sure, when its all in good working order. A good idea, but was executed like a Rube Goldberg contraption. :roll: Lots of crap going on, just to do one job. Over-engineered. Put the one-piece shaft in, plate 'er off and call it a job. ;) Might lose some fuel milage (Yeah right, already driving something with the areodynamics of a brick). You'll be fine with the one-piece. Rob L. :thumbsup: Link to comment Share on other sites More sharing options...
Geonovast Posted July 12, 2009 Share Posted July 12, 2009 The CAD was just Jeeps way of eliminating rotating mass in the front, like selectable hubs would. By disco-ing the axle on one side, it stops the inner half of the P/S axle from spinning, and allowed the D/S shaft to just rotate the spider gears and not the whole carrier. Which in turn, would keep the front driveshaft stationary. Not quite. All it does is prevent the DS and carrier from spinning. It does this by making the inner axle shaft spin just as fast as the outers, but in the opposite direction. It's amazing Disco D30's don't eat those needle bearings like candy, and go through spiders more often. Really the only advantage of keeping the CAD I can think of is to set it up to a manual actuation system, essentially twinsticking the truck without heavily modifying the T-case. Sometimes 2lo would be nice. Link to comment Share on other sites More sharing options...
Automan2164 Posted July 12, 2009 Share Posted July 12, 2009 The CAD was just Jeeps way of eliminating rotating mass in the front, like selectable hubs would. By disco-ing the axle on one side, it stops the inner half of the P/S axle from spinning, and allowed the D/S shaft to just rotate the spider gears and not the whole carrier. Which in turn, would keep the front driveshaft stationary. ...Not quite... Just have to rain on my parade... :( Rob L. Link to comment Share on other sites More sharing options...
Geonovast Posted July 12, 2009 Share Posted July 12, 2009 Just keepin ya on your toes. :thumbsup: :banana: Link to comment Share on other sites More sharing options...
Automan2164 Posted July 12, 2009 Share Posted July 12, 2009 Just keepin ya on your toes. :thumbsup: :banana: Thinking about it now, I don't know why I didn't put that on my post to begin with. Afterall, the inner shaft and the D/S shaft are still connected by spiders... :fool: . But the fuel saving idea is where they were going, but overshot a tad. At least I got that right. And 2 Lo is nice to have but something tells me Jeep didn't put in the CAD for that possibility. ;) Rob L. Link to comment Share on other sites More sharing options...
xjman4 Posted July 12, 2009 Author Share Posted July 12, 2009 wow you guys ROCK!!!!! thanks so much for the much needed lesson :D Link to comment Share on other sites More sharing options...
mvusse Posted July 12, 2009 Share Posted July 12, 2009 I wouldn't buy a kit. Get a shaft from the junkyard, use a jigsaw to cut a piece of steel using the vacuum disconnect housing as a pattern, drill 4 holes and (with help of some RTV to seal it) bolt it on using the original bolts. If you get an ABS shaft, or 97 and newer you will get the larger u-joint as a bonus. Just beware with an ABS shaft the ABS ring may have to be cut off to fit in your hub. 2 minutes work with an angle grinder and a cold chisel. You will have to pull the carrier out of the differential to install an oil seal in the axle. Stock replacement non disconnect seal will not work. My build thread (link is in my signature) lists one that works as I just went through this a month or so ago. I paid $15 for the shaft, $30 for a Spicer 5-760x u-joint (40% stronger than a 5-297x). Autozone carries lifetime warranty u-joints for about $15 if you're not worried about trying to be bullet proof. Already had the RTV, but a tube is about $4 or so, piecd of steel is just a few inches in size, I'm sure you can find something somewhere. I used 1/4" hard steel because that's what I happened to have laying around, but that's overkill. And about $10 for the oil seal ordered from NAPA. Link to comment Share on other sites More sharing options...
Pete M Posted July 13, 2009 Share Posted July 13, 2009 I wouldn't even do that if I didn't think I needed the strength of the bigger joints. It's super easy to simply open the cover, slide the locking collar on the axle shaft over to the "lock" position, retain it using any one of the various ways people have figured out, then put the cover back on and remove all the vacuum lines (making sure to cap them at their source).Done and done. :thumbsup: Link to comment Share on other sites More sharing options...
xjman4 Posted July 14, 2009 Author Share Posted July 14, 2009 cool, thanks guys :D Link to comment Share on other sites More sharing options...
Recommended Posts
Create an account or sign in to comment
You need to be a member in order to leave a comment
Create an account
Sign up for a new account in our community. It's easy!
Register a new accountSign in
Already have an account? Sign in here.
Sign In Now