4wd not engaging all the sudden

[Whitaker717]

Hi guys, woke this morning to some snow and ice and when I kicked it in 4wd my light didn’t light up and feels like it isn’t engaged. Where can I start to see what in the world is going on? It worked the last time I used it say a month ago. 87, 4.0. Thanks

[gogmorgo]

What do low range and neutral do? If it’s parked with the shifter in 4x4, can you spin the front driveshaft? If no, safe to say the CAD isn’t working. If you can rotate the driveshaft, something’s going on with the transfer case or shift linkage. But my money’s on the CAD. Most likely you’ve got a vacuum leak somewhere. If you want to lock the CAD in permanently it’s quick and easy, but does come at a very slight mpg penalty. Slight enough you probably won’t notice if you’re not religiously keeping track. 

There’s a couple write-ups on it in here:

 

 

[Whitaker717]

1 hour ago, gogmorgo said:

What do low range and neutral do? If it’s parked with the shifter in 4x4, can you spin the front driveshaft? If no, safe to say the CAD isn’t working. If you can rotate the driveshaft, something’s going on with the transfer case or shift linkage. But my money’s on the CAD. Most likely you’ve got a vacuum leak somewhere. If you want to lock the CAD in permanently it’s quick and easy, but does come at a very slight mpg penalty. Slight enough you probably won’t notice if you’re not religiously keeping track. 

There’s a couple write-ups on it in here:

 

 

So I put it in N and 4L and nothing. Peeled out and just the rears spun. At that point I just put it back in 2WD

[gogmorgo]

Did it seem like 4lo and neutral were shifting you into the ranges you selected or no? If yes, it would indicate the shifter and selector inside the transfer case were doing what they were supposed to, strongly pointing towards the CAD. If the shifter doesn’t seem like it’s doing anything, would most likely be a linkage issue. 

[Whitaker717]

7 hours ago, gogmorgo said:

Did it seem like 4lo and neutral were shifting you into the ranges you selected or no? If yes, it would indicate the shifter and selector inside the transfer case were doing what they were supposed to, strongly pointing towards the CAD. If the shifter doesn’t seem like it’s doing anything, would most likely be a linkage issue. 

Thanks for the tips. After monkeying around and looking it appears one of the lines was disconnected somehow. Plugged it back in and now it works again. I must have missed it somehow earlier. Thanks for the help!

[Pete M]

and that's why the CAD-bypasses are popular.  

[cruiser54]

This^^

[Whitaker717]

15 hours ago, Pete M said:

and that's why the CAD-bypasses are popular.  

I may give this a try Pete. I’m not sure I am skilled enough. Lol. Quick question on that, it doesn’t leave 4WD engaged all the time does it?

[cruiser54]

Hey, If me and Pete can do it, it's gotta be easy.

 

And no, 4wd will not be engaged all the time. 

[Pete M]

4wd is controlled by the giant lever by your knee.    eliminating the CAD only makes it like any 91+ XJ.    (aka: it makes it into a "solid shaft" on the pass side)

[Whitaker717]

17 hours ago, cruiser54 said:

Hey, If me and Pete can do it, it's gotta be easy.

 

And no, 4wd will not be engaged all the time. 

Lol. Thanks Cruiser. I may give it a try

[cruiser54]

15 minute job. 

[gogmorgo]

Locking the CAD in permanently just means the front driveshaft will be turning with the front wheels. This does have a very small effect on your MPG. You’ll also notice if there’s play in the front driveshaft u-joints or CV centring ball at highway speeds which might lead to new vibrations unless you were already ocaisionally rolling at highway speeds in 4x4. Which, well, don’t.