4WD Not Working

Hey, I have been having trouble with 4WD engaging on my 88XJ with a non-disconnect d30. It used to work okay on engagement, but wouldn't disengage for a while. It sounds like a vacuum leak, anyone know what I should start looking at first. I don't really have money for the cable engagement, but I think I might have to. I would like to get this fixed, seeing as it caused me to get stuck twice yesterday, the first time I could pull out in 2wd low, but had to be pulled out of an embarrasingly shallow mud puddle the second. Any advice would be helpful.

Well with a non disconnect D30 a vacuum leak really isn't an option...

Sounds like youhave a NP242 transfer case -- if left un-used they do tend to get a bit sluggish on shifting in/out of "part-time" 4wd. They also will slow-shift with worn fork pads and dirty fluid (especially after the fluid has had time to deposit on the rails.)

I'd recommend draining and reflilling your t-case and examining what comes out -- (should be pretty ruby red) ...

I think you intended to say you have a disconnect D-30. Check the vacuum line going to the axle, and if that looks good pop the cover off and see if the fork/sleeve is binding somewhere.

Yeah, it is a Disconnect, sorry. It has a np231 T-Case. How would I tell if it is binding, just try to engage it with the cover off?

Mich88XJ,

I had this problem on my 88 XJ. You need to go to the dealer and buy the vacuum harness for the axle shift motor.

The one bad thing about the disconnect axle is the shift motor is located underneath the oil filter mount. With the oil filter installed bottom down then every time you remove the filter you drip oil on to the shift more and the vacuum lines.

If you examine the black rubber portion that attaches to the shift motor it is oil covered and what I thought was a good vacuum seal is actually a leak.

So replace the shift motor harness, it runs around $10, and that should solve your problem and the "part time" light should come on when you pull it into 4-hi.

Also after you do this job you may want to spend the better part of a $100 bill and replace that vacuum harness under the hood. When I got my XJ with 100,000 miles mine was still factory. I changed the PCV valve and this harness, solved a bunch of vacuum leaks and the XJ had a better idle.

Martin

That sounds good, I have been having some idle problems lately also, and that is another possibility to fix them. I know the rubber lines looked okay, but they were a little dried out. I was going through the 4wd hardware catalog and looked at the parts for the axle, but did not see the harness. The closest thing I could see would be the motor assembly that includes the gasket, fork retainer clips, cover bolts and a washer. Is this what you are talking about since all the vaccuum lines run into it? I don't think it is because it is $75, but the only thing that I could see that was around $10 was the housing cover.

Mich88XJ,

Yes, this line connects the vacuum shift motor to the metal vacuum lines. It is approx a foot long. Any dealer parts guy should know exactly what you need.

There is a test you can to with a vacuum pump to see if the shift motor engages and disengages. It requires the front axle to be off the ground and then you turn the left front wheel to see if it engages or not.

HTH

Martin

Hey, thanks! I am going to let my friends dad know what part I need, and see if he can get a discount since he works at a Chrysler dealer. I hope this is it, what are the chances that the shift fork for it is binding? That is just what someone else mentioned. Anyhow, so correct me if I am wrong, I am replacing the rubber hoses that connect to the plastic vaccum lines, and also the harness? Anything else, and anything special that I may need? Thanks, and I will let you know what happens.

Mich88XJ,

When you get the new vacuum harness you will know what to do with it. On one end is this fitting holding the 3 plastic hoses. The other end has a big rubber piece which 2 of the plastic lines connect and then the third line is sepearate. Then the 3 plastic lines are wrapped in that black plastic conduit for protection.

This piece connects the shift motor to the metal vacuum lines of the chassis. This part will swap out with what you already have, there nothing to rework but it may be good to wipe off the nipples before you attach the new harness.

Martin

Okay, its been a while, and I haven't got the chance to go and get the vacuum harness yet seening how close it is to graduation I have been a little busy. Anyhow, yesterday on my way to work I was driving along at about 35 mph with the heat on (because the engine has been running too hot (great, another problem!)) and all of a sudden there was this loud whining sound with a little grind in it, so I started slowing down quickly, and all of a sudden there was a big "thud" so I slammed on the brakes and pulled off the road. Then I noticed that the part time light was on, but the t-case was in 2wd. After getting to work, I shut the Jeep off, and when I restarted it, the light was off. Anyone know why it would do this, I need to fix it so that it doesn't break anything (if it hasn't already).

check your linkage...


if that is ok then try this
1. put it in 4wd... drive around a bit.
2. stop and switch the vacuum lines around on the actuator motor so the motor will engage when placed in 2wd.
3. start driving and put it in 2wd.
4 stop the motor put it in 4wd
5. Switch lines back and start again

if it is in 4wd now then you have a bad vacuum line on the actuator. I had to do this to mine to get it to work and now it works fine. The idea is that the normal vacuum used to disengage the coupler will instead engage the coupler and you will have 4wd. I had to do this 2-3 times before it would work normally. It is a lot easier than pulling the shift motor and manually doing it.

This may not work for you but it is worth a try.

Okay, I will try that, but would this cause the engagement of 4wd without me doing anything, plus, what would make the whine and then the thud? Anyhow, if I want to check this, what hoses on the vacuum motor are for engagement and disengagement? BTW, did you get my e-mail about the seats?