4 wheel drive

[jeep stuff]

i can't figure out why my 86 comanche 4x4 won't engage it goes in 4 low but its till 2 wheel drive anyone have any ideas

[Jerry]

Suprised no-one has responded to your question yet!

 

I may be entirely wrong but try examining your Central Axle Disconnect

http://www.comancheclub.com/forums/viewtopic.php?f=2&t=17533&p=178077&hilit=central+axle+disconnect#p178077. Vacuum lines could be split or it could just be stuck. Try putting it in 4x4 and driving around a bit, it may unstick itself.

 

WELCOME BTW! :cheers:

[jas2861]

There are a couple of things....

1. Check your vacuum lines coming from the transmission up into your engine by the fire wall. These should be a couple of different colors and be hard plastic. Look for breaks, cracks, or maybe they just came out.

2. Check up on your front axle by the actuator. There is a connection that comes undone that you may need to plug back in.

 

Hope that helps.

[freakjeep93]

welcome to the club :waving:

iout of my leugue but now that i think of it they have good ideas :agree:

[Pete M]

Yup, sounds like your CAD (central axle disconnect) system isn't engaging. It's a very common issue caused by poor engineering. One easy and permanent fix is this:

viewtopic.php?f=9&t=18415

 

The CAD is essentially a 2-piece axle shaft on the front passenger side with a sliding collar to lock it together. Your transfercase is likely sending power to the front axle, but without the CAD locked, no power can get to the wheels. If you lock the CAD permanently, your truck will function just like any Jeep since the early 90s (when Jeep eventually did away with the crappy system in favor of a one-piece axleshaft).

[jeep stuff]

thanks i hope that works

[socal1200r]

Okay, my newbieness to the 4wd community will show here. What are the preferred procedures for operating the 4wd system on a manual trans MJ? I've heard that some 4wd systems you have to drive in reverse for several feet to engage/disengage the 4wd, some you have to be completely stopped, etc. So how about it, what's the step by step for proper usage of our 4wd systems, and what to listen/look for to make sure it's working the way it's supposed to?

[jeepcoma]

what's the step by step for proper usage of our 4wd systems, and what to listen/look for to make sure it's working the way it's supposed to?

 

Just pop it into 4H while you're neutral on the throttle. You can switch back and forth between 2H and 4H while stopped or in motion (if you're easy on the throttle; you shouldn't slam it in while you're accelerating or on the brakes). Come to a stop for 4L. You'll feel it drive and steer differently once 4wd is engaged, it will want to pull you to straighten out, but with an open front end it won't be huge. Hit pavement in 4wd and it will feel all wrong straight away (make good use of that shift-on-the-fly 4wd and get it in and out as necessary).

[Oizarod115]

i believe our "shift on the fly" 4wd is good for 2h-4h-2h shifts at speeds UP TO 40mph, so if yuo're turning onto a dirt-road at 20-30 and pull it into 4wd between shifts it'll be just fine.

[Geonovast]

Lock the CAD and be done with it.

[socal1200r]

Lock the CAD and be done with it.

 

So if I'm following this correctly, locking the CAD and "disabling" the vacuum-assist will ensure that the lever in the cab will positively engage and disengage the 4wd system?

[Geonovast]

Lock the CAD and be done with it.

 

So if I'm following this correctly, locking the CAD and "disabling" the vacuum-assist will ensure that the lever in the cab will positively engage and disengage the 4wd system?

 

Correct. Jeep did away with the CAD by the end of 93 anyway, and all Jeeps with a 228/229/242 have a non-CAD 30 as well.

[socal1200r]

Lock the CAD and be done with it.

 

So if I'm following this correctly, locking the CAD and "disabling" the vacuum-assist will ensure that the lever in the cab will positively engage and disengage the 4wd system?

 

Correct. Jeep did away with the CAD by the end of 93 anyway, and all Jeeps with a 228/229/242 have a non-CAD 30 as well.

 

One more thing...in the thread that Pete linked to, the pics show the front axle being up on jackstands. That's not really necessary to do this mod, right? There should be enough room underneath to remove that cover and slide the collar over, move the fork over in the cover, then re-attach and be done with it? No mention was made of gaskets, so does care need to be taken when removing the CAD cover, or just make sure I clean the mating surfaces and put down some RTV, or?

[Geonovast]

No need to be on jackstands, as you can line everything up by turning the driveshaft by hand.

 

There is a gasket there. When I did mine, I just pulled it off, left the gasket on, and didn't bother with RTV when I put it back on. Just wiped it down, and bolted it back on.

 

Just beware you're going to lose fluid when you do this. I avoided that because my axle happened to be off of the vehicle when I did it, so I simply rolled it forward.

[socal1200r]

No need to be on jackstands, as you can line everything up by turning the driveshaft by hand. There is a gasket there. When I did mine, I just pulled it off, left the gasket on, and didn't bother with RTV when I put it back on. Just wiped it down, and bolted it back on. Just beware you're going to lose fluid when you do this. I avoided that because my axle happened to be off of the vehicle when I did it, so I simply rolled it forward.

 

When you say, "line everything up", what are you referring to? So this isn't as simple as removing the cover, sliding the collar over, moving the fork in the cover over, then putting it back on? Are we talking something similar to lining up timing gears, should I mark them before I start messing with the collar? What would have to be lined up by turning the driveshaft? And since the 4wd isn't engaged, the driveshaft should turn "by hand"? As for the fluid loss, I suppose I could put some gear oil back in thru that upper bolt on the CAD cover?

[Geonovast]

There's splines on both shafts for the CAD. They have to be lined up in order for the collar to slide over.

 

You can refill the fluid through the plug in the diff cover. The fluid runs through the axle tube from the diff to the CAD.

[socal1200r]

Okay, followed the pics in Pete's thread: disconnected the three "tubes" going into the end piece of the CAD cover; removed the CAD cover; lined up the shafts and slid the collar over the shaft; removed the c-clip and shifted the fork over in the CAD cover, put the c-clip back on, plugged the three hose ends on the cover, and put the CAD cover back on; removed the front diff fill plug and topped off with gear oil; zip tied all three tubes up and out of the way.

 

I played around with the lever and put the MJ into 4H and 4L in the back yard, and noticed something right away. Before I did this mod, when I pressed in the clutch, the truck would still roll a few feet, like a "normal" 2wd truck would do. Now, even with the lever in 2H, it stops rolling right away. Is this because I locked the CAD and it's normal, even though it didn't do it before, or is it "stuck" in 4wd now?

 

Hopefully this is "normal", and I'll just have to get used to it. But it definitely didn't do that before, so I just want to make sure I did this right, and everything is working the way it should.

 

UPDATE - just drove it on the street for a few miles, and I think all is well. There doesn't seem to be a big difference between how it drives in 2H or 4H, just a little more gear noise from the front. But when I pulled over and stopped, put it into 4L, and took off, yeah, it's in 4L, that's for sure. So it seems to move between 2H - 4H - 4L and back as it should, all thru the lever. So I'm guessing I did this mod correctly, and everything works the way it should.