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HELP! 4HI and 4LO won't engage

AlabamaDan

NAXJA Forum User
Location
Heart of Dixie
I took my xj out this weekend and just after leaving the road I hit some mud. I almost instantly got stuck. I shifted the Tranny into N and pull the 4x4 lever into 4LO and nothing changed. I finally stuck my head out the window and noticed the rear wheels spinning and the front wheels just sitting there. I'm assuming that means my 4wd wasn't engaging.

So is it that my 4wd wasn't working? How can you really test your 4hi and 4lo to see if it works?

Assuming it isn't working, where can I find a troubleshooting list? Is it possibly something simply like a vacumn hose?

Please help guys. I'm very bummed.
 
if you have the little vacume lines running from your tcase to your front axle, this is on older jeeps it is the vacum disconnect if it is unplugged just plug them back in.
 
CanMan said:
You subscribe becasue you already posted. ;)


What year? What TC?

Have you checked out the linkage, incase it is out of adjustment?

I have an 88 XJ.

AW4 Tranny
NP242 transfer case

I don't know what to look for in the linkage. I've been searching for a diagram or something in the FSM, but can find anything helpful. I can crawl underthere tomorrow, but I'm afraid I won't know what I'm looking at.
 
you have a vacuum disconnect axle. most likely the little actuator on the axle is bad if your lever can move easily into all the postions. on the passenger side of the axle youll see a little boxed area. thats the vacuum actuator (egh, sp?) a lot of times its just the little diaphram inside it, just replace and have fun.

edit:
never mind, just read 242...

did ya check if your pass wheel was spinning... maybe you were just really stuck...
 
well first off, i believe you aren't fully aware how to use your 4wd. you can shift into 4hi while moving, and only need to stop and put it in neutral for 4lo.

if you really wanna see if your 4wd is working, get yourself 4 GOOD STRONG jack stands and position them under your axles. 2 in the front and 2 in the rear. make sure you have them positioned properly directly under the axle, and as far out as possible. also make sure that the vehicle is almost level front to rear. after you have the entire vehicle on 4 jackstands and are 100% confident that it won't move, start it up in 2wd and put it in Drive. then engage 4HI, get out and look at your tires and driveshafts and see what they are doing.

also remember that if you have open differentials (which you probably do), that only 1 front tire will turn. and if you try to stop it, the other one will/should start turning instead.
 
scorpio_vette said:
well first off, i believe you aren't fully aware how to use your 4wd.

Maybe. I'm won't argue that I'm not fully aware of how to drive off-road. But...

scorpio_vette said:
you can shift into 4hi while moving, and only need to stop and put it in neutral for 4lo.

Got that part.

So it could be that the front passenger wheel was turning and my 4x4 did work? I'll try the idea with the jackstands. I was actually thinking of that myself last night.
 
yea, jackstand idea is the easiest way to find out.

i was just putting up an option, since you were going through mud, its totally possible you got sunk in a rut, and you tires were spinning (with open differentials, when a tire has less traction, it spins, and the other does nothing...)
 
I've been reading and have a couple of more issues which may be symptoms. My AC/HEAT only works when the fan is on hi. Could hint to vacuum.

Sometimes the key doesn't want to come out when I put the car in park. The ignition switch won't go back far enough. I turn it back to "ON" and move the shifter back to 1st then up into Park firmly and it works fine. Could hint to linkage.

I'm gonna crawl under there in the morning and look around, make sure I have a NP242. Problem is that I'm not an expert on what I'll be looking at.

I don't have any indicator light(s) on the dash when I pull up on the 4x4 handle either.

I appreciate all the advice given here so far. Y'all are being patient with me.
 
One quick way to physically see if you are in 2wd or 4wd is to put your hand on the front driveshaft and rotate the shaft. Try it in 2wd, it will rotate, then shift the linkage into 4hi, should now be tight and not rotating, indicating that the t-case is shifted. If not, it is time to get familiar with adjusting the linkage.
 
Lodi Jim said:
One quick way to physically see if you are in 2wd or 4wd is to put your hand on the front driveshaft and rotate the shaft. Try it in 2wd, it will rotate, then shift the linkage into 4hi, should now be tight and not rotating, indicating that the t-case is shifted. If not, it is time to get familiar with adjusting the linkage.

that would also only work if the tires are off the ground. but yeah that's another way to test it.



your heat only working when the fan is on hi, is either the switch or the blower motor resistor. the only part controlled by vacuum are the settings for defrost/heat/vent.

if you have a 242, the front axle won't be vacuum controlled, and if you have a 231, then i may or may not be. if you crawl under the drive side behind the tranny cross member and look at the t-case where the rear driveshaft comes out, there should be a round metal tag. if you clean it up, you'll see the model number. it'll either say 242 or 231.
 
Finally got time to crawl under. (I work too much.) It turns out I have a NP231! I assumed 242 because of the year, but it's a 231. It has four little wires/tubes coming out of this module beside the ID tag. They're colored. I'm assuming that those are vacuum hoses and each color does something different. Could anyone explain those to me? How do I test them?
 
ok the simplest test would be to carefully unplug the vacuum connector at the transfer case, and use a fine tipped blow gun and air compressor to blow in each line. if you don't hear a major hissing somewhere along the vehicle, then it's probably good. just make sure you don't use full pressure around 10-15psi should be good.

then there is also the possiblity of the vacuum motor/accuator in the front axle not engaging, and that's why you don't have 4wd.
 
Dan,
What part of the State are you in? If you're in the H'ville area, you could holler at myself or I could point you in the right direction, probably...

If you're around Birmingham, there are several people here or on CAOS who can help... don't know about south of there, though.
 
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