Jeep Wrangler Forum banner
  • Hey everyone! Enter your ride HERE to be a part of September's Ride of the Month Challenge!
1 - 14 of 14 Posts

·
Registered
Joined
·
13 Posts
Discussion Starter · #1 ·
So again, just got my jeep.....94YJ 4.0 6 cyl manual. 4WD won't engage. 117,000 miles, woman owned since 94. Never off road. Light comes on in dash, smooth shift into 4wd, no noise. But drive shaft is not turning. Jacked up driver front wheel, put in 4wd and I can still turn wheel freely by hand, so it's not locking in. Took off CAD and checked vacuum lines. Seems good. Fork moves back and forth while shifting but still not engaging. Drained transfer case last night to see if I had any metal fragments in it. Fluid looked good as new. I've been told the linkage could be out of sync on t case or even though the CAD appears to be working, it could have a leak and not have enough pressure to shift far enough to actually engage. I thought if the 4wd dash light comes on, the vacuum was good? Am I wrong? I am wondering how it could be the t case since it has fairly low mileage and this woman never took it off road. Any opinions and ideas on what to check or do would be greatly appreciated. I'm beginning to lose sleep over this. lol
 

·
Registered
Joined
·
879 Posts
the light just means you have vacuum to the switch, the actuator is probably not holding enough vacuum to shift
 

·
Registered
Joined
·
13 Posts
Discussion Starter · #3 ·
I hear the diaphragm thing can get worn out. Is it sold separately or do I need to replace the whole thing?
 

·
Premium Member
Joined
·
10,093 Posts
#18 on the list comes as a kit $85

Jeep® Wrangler YJ Axle & Differential Parts - Quadratec

There are other solutions that are cheaper, you can lock the fork over several ways and it keeps the front shaft turning or you can install a posi lock cable for $150. Your choice stock vacuum or the alternatives.
 

·
Registered
Joined
·
4,757 Posts
It could be the shift linkage. It might be moving enough to engage the vacuum lines but not going all the way into gear.

Pull the lever into 4wd, and crawl under it to see if you can turn the front driveshaft by hand. If its in 4wd the front shaft should be solid. If it still spins, then i would bet on the linkage needing adjusted.

To adjust the linkage, under the jeep on the rod that runs from the 4wd shifter to the first place that it pivots, you will see a bolt in a square clamp, I believe in the newer ones its 10mm. Might be 12mm. Make sure you are in 2wd, loosen that lock bolt, and go inside the jeep and push the 4wd shifter all the way forward, or have someone hold it forward and tighten the lock bolt.

If that doesnt work, then its a much harder issue, such as the chain in the t-case.

But that linkage is a common flaw in the YJ design and most likely the case.
 

·
Founder, ThumbJeeps
Joined
·
4,062 Posts
^ yes!

and, be sure once you get it fixed to use it frequently if you can... not being used may be why things are sticking.
 

·
Registered
Joined
·
259 Posts

·
Registered
Joined
·
523 Posts
1Junior said:
Also there is a "FREE" fix that can be found here on our forum it is http://www.wranglerforum.com/f8/vacuum-shift-motor-inexpensive-fix-87568.html I was able to do this in a matter of 15 minutes with simple hand tools and have had no issues with it since and hasn't seemed to effect the driving at all on the highway
I just did this today and it was very easy the hardest part was the e-clips and that included all four bolt heads breaking on me
 

·
Registered
Joined
·
13 Posts
Discussion Starter · #11 ·
Thanks for all the advice! I think I will try the linkage tomorrow. Am I wasting my time messing with the CAD since the light comes on and the fork moves? Should I be focusing more on the t case since the drive shaft isn't turning when jacked up? Or is it still possible the CAD is leaking and not holding enough to pressure to engage. The what? makes the drive shaft thingy turn like it's supposed to????? I'm about to" blow a gasket" trying to pinpoint my problem. Is it really possible the t case could need replaced since it's only been in 4wd during a few snow storms? I'm having a really hard time grasping that. But then again, I've never owned a Jeep before. That's why I love this forum. I am learning a lot!
 

·
Registered
Joined
·
879 Posts
the easiest way to confirm if the tcase and linkage are good and vacuum or cad is bad is to lock the fork over manually and see if 4wd works
 

·
Registered
Joined
·
13 Posts
Discussion Starter · #13 ·
Well that sounds simple enough. Thank you! Looks like I will be taking the cad off again tonight. Should prob just replace the darn thing either way.
 

·
Registered
Joined
·
523 Posts
I would do the vacuum mod that coyote shows step by step I did that yesterday and total time was less then an hour and it cost 6$ for the rtv gasket stuff and like 1.44 for 4 bolts and the spacer
 
1 - 14 of 14 Posts
Top