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4WD Not Engaging... WHY?

NeXJ

NAXJA Forum User
Location
Los Angeles
This is very peculiar... granted the XJ's been sitting for a year or two... but I've got a lot of work done on it now and it's been resuscitated as the daily driver... I just fixed a problem with having the reverse light switch connector and the 4WD full time light connector and wanted to make sure that the 4WD light came on properly... so I fired it up in the parking lot and engaged 4H and 4L - and NOTHING - so then I figured I'd drive a few feet in 4H and get it to engage. Nothing. 4 LOW - NOTHING. It seems to refuse to engage as if I weren't doing ANYTHING..

Should I check my linkage? Suggestions???
 
92 w/NP-231.... yes I know if the vac lines are blocked it can create a problem... though I guess I'm not sure how to test them.. remove them and blow through them...??

Though there's ZERO engagement at ALL... I would THINK that even if the vac lines WERE blocked there would be SOME degree of beginning of engagement...? That's why I was asking about the actuator/linkage to the NP231...

the tranny is an AX-15 by the way... not that it should matter...
 
Ok, vacuum is probably NOT your issue. XJs with the NP231 through 1991 were equipped with the D30 CAD axle--vacuum motor on the passenger's side of the front axle. No vacuum, no 4wd.

Now, take a look under your front end, passengers side of the axle--do you have a vacuum motor there?

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Post up what you find.
 
Hmmm.... after cursory examination with a flashlight (in the dark) I found NOTHING... I remember reading MANY posts years ago about the infamous D30 vacuum disco... and, well, I can't recall exactly... but I remember thinking mine didn't use that system (?) - but it's unreliable info... at any rate - mine's a 92 sport package that had full skid plating etc (sort of an unusual package)... I'll take a better look tomorrow and try to follow the vac lines from the transfer case. Unless my disco is on the driver's side somehow (didn't look there).
 
Though it's quite possible the linkage got munged up too... I haven't checked that - as I haven't had anyone around to check if the shifter is physically connected to the actuator via cable... it doesn't feel like it... even when the motor's off... I don't hear any sort of metallic noises coming from under the vehicle... so i'll do that when I can find a 'victim' to help me out... but for now I wanted to see what the likely suspects were...
 
Oh yeah... one more thing.. I forgot to mention it earlier... when I shift into 4 LOW I don't even get any kind of gearing change in the rear... regardless of whether or not my front end is engaged... so that's why I'm almost thinking along the lines of seized cable or messed up linkage (also had a budget shop replace my e-brake recently - so I wonder if they messed something up too!)
 
None. Up through 94 or 95 the transfer case switch still used vacuum up to the passenger's side firewall to a vacuum/electric switch for the dash light, but after 91 the axles are all without disconnects.

So, you still have 2wd in all positions? If so, the linkage must not be connected.
 
Okay- update... I was playing around with the 4WD lever in the parking lot again... and think I managed to get it into 4LOW... I definitely noticed that the neutral position on the 4WD lever resulted in not moving at all while in reverse and first gear. I'm pretty sure I got into 4LO though... but I didn't wanna push it as the surface back there is pretty grippy.

ALSO - only got the part time light to come on for a sec when I was in neutral and I was toggling the lever side to side... any idea what that means...? Isn't the P/T light supposed to indicate 4HI and the F/T light 4LO?

at this point I'm starting to think I only have a rusty/sticky shift cable to the t/case maybe (??)
 
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Ok, lets take a step back.

NP231 Part-time only: 2wd/4hi/N/4lo

NP242 Full-time and Part-time: 2wd/4hiPT/4hiFT/N/4lo

Which have you got?
 
Hi joe.. well obviously the first one... I was asking only because I just had my face buried in the FSM and was looking at the indicator light array for some clues to another problem... sorry to confuse by throwing that out there... I just couldn't remember whether it was the PT, FT or both lights that come on...
 
Ok, your light--when properly working--would be on in 4hi and 4lo.

Often times the ball/plunger on the switch will gum up and stick, or the legacy vacuum line to/from the switch will head south and of course the bulb in the dash could go. I haven't seen a single vacuum/electric switch on the firewall go bad, so far.
 
should i hit the linkage at the NP231 with some WD40 or something? other suggestions..? I guess just start using it more, too, huh? just curious about the intermittent light... though maybe the connectors could use some contact cleaner...
 
I'd totally forgotten what those terms meant... since I'm (like most of you) mired in the minutiae of U-joints and gear ratios and locker engagement etc... so I had to look up those terms! What a silly and not-very-useful designation...!

Can anyone suggest (as I asked earlier) a good maintenance routine for cleaning up the linkage and actuator on the NP231...? There's a TON of crap under there... maybe 4mm-5mm of soot (seriously) - Los Angeles seems to do that. There's a great little garage I go to that has a rig for doing gasoline pressure washes (for engines and the like) - recommended?
 
Yeah, pressure wash is good. Make sure that the engine compartment area around the throttle body in particular remains off limits, the TPS hates getting wet and will die on you.

Other than making sure the nylon bushings haven't deteriorated and that the adjusting trunnion and its locking bolt haven't rusted in place the rest of the stuff should be in pretty good shape, not being in the rust belt.
 
Yeah breaking in the last TPS I put in wasn't so much fun... driving around with my engine screaming for 20 mins...!! don't want any more of that!!!!
 
I had a similar problem and part of the linkage to the transfer case had come disconnected. Have someone shift from 2wd to 4wd while you are under the Jeep looking at the linkage to see if you can find any problems.
 
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