Center Axle Disconnect: How does it work?

[mooktank]

Ok so I finished putting my cummins b3.3 engine in my explorer. I'm using a jeep AX-15 transmission and np231 tcase. My explorer is a 1995 with the CAD vacuum disconnect. Right now I'm running a tiny vacuum pump for running my HVAC controls.

I'm trying to get my 4x4 working. I have a manual case so I know the case is engaging. The CAD is not engaging however. I have the vaccum pump run to the lines for the CAD but I assume the electric solenoids are not diverting the vaccuum to the correct side of the diaphragm when i turn on the 4x4 switch or maybe not at all.

I sort of want to just lock the thing permanently either mechanically or by just putting vaccuum on the proper side the only problem is I don't know which way the mechanism moves to lock the two axle halves together. I suppose if this doesn't work properly I could just grab a diff from a newer truck.

Any insight?

PS if you want to check out my cummins conversion I have it on my blog at www.mooktank.com

 

[MountaineerGreen]

You can convert to a live axle easily, they bolt in 100%.

There is a good thread on the front diff http://www.explorerforum.com/forums/showthread.php?t=88718

 

[Cstoliker]

Here is a nice how to on the CAD.

http://www.explorerforum.com/forums/showthread.php?t=88718

 

[MountaineerGreen]

You can convert to a live axle easily, they bolt in 100%.

There is a good thread on the front diff http://www.explorerforum.com/forums/showthread.php?t=88718

Here is a nice how to on the CAD.

http://www.explorerforum.com/forums/showthread.php?t=88718

Same Link

 

[Cstoliker]

Yes.. lol sorry

 

[mooktank]

Thanks guys that thread looks like it has some good info! I guess I will just try to see if my little vacuum pump will be enough to actuate the CAD. I like the fact that a lunchbox locker can go in there without issues.

 

[Cobraguy]

Whatever you do, don't you dare leave this site without pictures of this conversion!!!

 

[mooktank]

Whatever you do, don't you dare leave this site without pictures of this conversion!!!

As soon as I'm completely finished I plan on doing a full writeup with mileage calcs etc. I will post it up here for sure.

In the meantime my website has pics of the construction phase, etc.

 

[Mbrooks420]

Awesome project, can't wait to see the pics. I've always thought a diesel would be right at home in the Explorer engine bay.

 

[JDraper]

Thanks guys that thread looks like it has some good info! I guess I will just try to see if my little vacuum pump will be enough to actuate the CAD. I like the fact that a lunchbox locker can go in there without issues.

Vacuum pump should work fine for it. It doesn't take much vacuum to move it. Easiest way would be to have an electrically operated SPDT air switch hooked to the vacuum pump so you can alternate which side of the air solenoid sees the vacuum.

Or, you could remove the vacuum operated solenoid and replace it with a 12V solenoid (like a door lock solenoid) and do it electrically.

 

[mooktank]

Vacuum pump should work fine for it. It doesn't take much vacuum to move it. Easiest way would be to have an electrically operated SPDT air switch hooked to the vacuum pump so you can alternate which side of the air solenoid sees the vacuum.

Or, you could remove the vacuum operated solenoid and replace it with a 12V solenoid (like a door lock solenoid) and do it electrically.

Something is up with it. When I turn my switch to 4x4 I can hear something move and when I put it back to 2wd the vacuum pump runs for a second. I'm pretty sure that means the solenoids are working and I'm guessing there is not enough vacuum to move the actuator. Either that or there is something wrong mechanically inside the CAD.

 

[JDraper]

Have you tried lifting the nose off the ground and spinning the wheels by hand? If the axleshafts aren't fully lined up when the actuator moves, it won't lock up the split. With the vacuum applied, you may have to rotate the wheel (or the inner axleshaft) a fraction to get it to drop in. If nothing is damaged, it may just need a cleaning. If it's gummed up, there may be enough resistance to keep it from working.

 

[Cobraguy]

I would also add a vacuum reservoir to your truck. In addition to the a/c reservoir. I think you're going to need it to smooth out all your vacuum operations and have a reserve.

I REALLY like the idea of shifting that electrically. Especially if you can find a very high quality solenoid that will live in the harsh environment. Not sure that is available though. Whatever you do, don't even think about the old Chevy axle disconnects. They used heat to expand an actuator in their shifter and would fail damn near everytime it got good and cold out.

 

[mooktank]

I would also add a vacuum reservoir to your truck. In addition to the a/c reservoir. I think you're going to need it to smooth out all your vacuum operations and have a reserve.

I REALLY like the idea of shifting that electrically. Especially if you can find a very high quality solenoid that will live in the harsh environment. Not sure that is available though. Whatever you do, don't even think about the old Chevy axle disconnects. They used heat to expand an actuator in their shifter and would fail damn near everytime it got good and cold out.

What about shifting it with compressed air? I'm thinking maybe a cable shift but for now a set screw or something to keep it locked full time until I have time to make a cable shifter.

 

[JDraper]

EDIT: nevermind..was a bad idea...had a brain fart while posting. I'll post up later on what I think the best way to run it is. Got some ideas from working on it in the past.

 

[Cobraguy]

I'm not sure a door lock actuator would have enough torque. Do you think so? Maybe a screw operated one. But you are correct...it would DEFINITELY need to be protected from the elements.

Mooktank...I just went to your website. I am stunned. But if I may be so humble...it appears you need to change the pulley on your a/c idler/tensioner. It appears to be a grooved pully. You need a smooth one. The pulley by itself is cheap and available from many sources. The grooved one will destroy your belt fast as it's riding on the back of the belt.

 

[mooktank]

Mooktank...I just went to your website. I am stunned. But if I may be so humble...it appears you need to change the pulley on your a/c idler/tensioner. It appears to be a grooved pully. You need a smooth one. The pulley by itself is cheap and available from many sources. The grooved one will destroy your belt fast as it's riding on the back of the belt.

Thanks for the compliment. Yes I'm aware of the pulley issue. It's already starting to make the belt look not so good. I planned on turning off the ribs asap but if there's a place to get a pulley the same diameter and same bearing but smooth I'm all ears (or eyes).

 

[mooktank]

Thanks for the compliment. Yes I'm aware of the pulley issue. It's already starting to make the belt look not so good. I planned on turning off the ribs asap but if there's a place to get a pulley the same diameter and same bearing but smooth I'm all ears (or eyes).

For the record, I fixed that today with a file. A nice positive rake with the engine running and the grooves are gone. Who needs a lathe when you have an engine mounted in the truck. An "engine lathe" per se. lol.

I jacked up the front end and rechecked today. The axle halves are definitely not locking together. I'm going to tear into it this weekend and see what's going on inside.

 

[JDraper]

Hokay got some time to think on this. To make the system work properly, you have to be able to move the shuttle to either position, and hold it there. This makes an electric solenoid unattractive as you would have to have it constantly powered. Most electric solenoids have a duty cycle that doesn't allow for constant hold over an extended period of time. Therefore, running of either engine vacuum, a vacuum pump, or a mechanical cable assembly would be preferred as those won't overheat & burn out over time.

What I'd suggest for an easy way to do it is get the vacuum solenoid off the firewall of a '95-'96 Explorer and use that. You would then just need a good vacuum source and a spdt electric switch to operate the solenoid like I did when I figured it out the first time which is in the post you were referenced to above.