Hi I'm confused about the 4wd system in the xj. Since the transfer case is a chain driven where the output and input is always connected. What disengages the front axle in 2wd?

 

The engagement is inside the transfer case at the chain sprocket.

 

In 2wd the front wheels are driving the transfercase, in 4wd the transfercase is driving the front wheels. There is no power being sent to the front axle in 2wd, the stuff is just turning.

 

4x4jeepfan, do you have the 242 or the 231? There should be a "sticker" on the backside.

 

I'm still confused you guys. I don't have the jeep yet, I'm looking for one with np 231 command-trac. So the disengagement is in the transfer case?

 

First video I found, not vouching for it. Find a couple youtube vids and you'll get a good grasp I suppose. I remember back when I was completely lost now I'm partially informed due to CF and this thing they call the Internet.

 

I get it now. That is similar to how I thought it worked. But I couldn't find any information on it so I thought it was the front axle that disengages some how. Thanks you guys.

 

On the 1990 a and older there was a disconnect on the front axle. It was a collar that locked the two piece right side axle shaft together. It was vacuum operated and problematic at times. The only benefit to those older disco front axles was that the right side upper control arm mount was stronger than the later axle's control arm mount.

 

I heard of that. How does that stop the left side side axle shaft from moving? Or Does the older ones also disengage at the transfer case?

 

The left side still moves, but the spider gears are usually the only gears in the differential that are moving if the right shaft is disconnected.

 

But if there's no power going to the front in 2wd why did they do the 2 piece axle shaft?

 

I don't know, but I guess they realized they didn't need the disconnect and quit using it in 1991.

 

My guess would be they figured it would work like selectable hubs and give better fuel mileage in 2WD with the front axle disconnected. I don't think it actually did....Probably just Jeep engineers trying to "think outside the box", or toaster on wheels in the case of the XJ

 

^ Correct.