Front Diff Locked?

[Cmbechtold]

Mechanic sais my front diff are locked something to do with vaccum I guess? Any ideas?

[mvusse]

The vacuum lines control a central axle disconnect. This has the same effect as manually locking and unlocking the hubs on a Ford, but is done automatically by the transfer case using engine vacuum when engaging 4wd.

 

These lines do not lock the differential, though, they only engage the axle.

 

I would find a different mechanic. IOW, one who understands how mechanical systems work, which is supposed to be their job. Mechanics can't fix what they don't understand, and yours evidently doesn't understand even something as simple as how an axle and differential work.

[Cmbechtold]

Ok so any idea how to fix or what is wrong?

[Incommando]

The most common problem is a loss of vacuum. The easiest permanent fix is to by pass the Central Axle Disconnect ( cad) and have the shaft locked together all of the time.

http://www.cherokeeforum.com/f2/free-front-axle-cad-bypass-91-writeup-38589/

 

 

You can also buy or fab a cable system to make it work.

 http://4x4posi-lok.com/app_jeep.html

[mvusse]

Ok so any idea how to fix or what is wrong?

 

What is it or is it not doing?

[Cmbechtold]

It's locked in and won't come out as if it's in 4wd. What do you guys suggest just leave it locked in so I don't run the risk of it not locking back in? Or try to get it fixed?

[Blue88Comanche]

It's locked in and won't come out as if it's in 4wd. What do you guys suggest just leave it locked in so I don't run the risk of it not locking back in? Or try to get it fixed?

 

I would ensure the cad is in the locked position using the above provided link and keep it locked.

 

Now something that was not covered yet is, do you know if your diff has a locker installed?  It could have a lunchbox locker and that is what the mechanic was referring, along with stating the cad was locked.

[Cmbechtold]

How do I tell?

[Blue88Comanche]

How do I tell?

 

the best way is to remove the cover and if you get something looking like the picture below, you have a lunchbox locker.  Note the lunchbox locker replaces the spider gears

 

and this as the inside of an open diff with the stock spider gears

 

if you don't want to remove the cover, make sure the TC is set for 4wd.  lift the axle high enough so the wheels spin freely.  Now spin the tires if the other tire spins in the reverse direction then you should have an open diff.  to test functionally of an auto locker may require two people. spin one tire till it stops and hold it, then spin the other tire the same direction till it stops, next spin one tire in the reverse direction, it should not stop and you should hear a ratchet type sound coming from the diff.

 

 

Edit:  If you do remove the front diff cover get a picture and post it if you are still having trouble. 

[Cmbechtold]

Ok thanks

[cruiser54]

Do the CAD delete yourself and don't go back to that mechanic.