Ignorant and worried - '97 ZJ Laredo

[DarinM]

My inlaws just gave us a 1997 Grand Cherokee Laredo with Selec-Trac and the I-6. 151,xxx miles overall in really good shape.

It's been well maintained. They told us of a couple electrical issues - some kind of onboard computer thing that is dead and it also occasionally dies temporarily but will start again after a bit. I've been researching this and I think it's probably a crankshaft sensor or something that should be easy enough to fix.

We got the Jeep yesterday and drove it around a bit. Seemed OK - but I don't think the transfer case is disengaging. It seems as though it's always in 4 wheel drive no matter where I put the lever - more research to be done on this as I have time.

I drove it to work this morning and now I'm learning about my ignorance. I have about a 50 mile commute to work. When I pulled off the highway onto surface streets, I noticed quite alot of smoke coming from under my new/old vehicle. Crap!

I pulled into a nearby parking lot and looked under it to see oil on the rear of the vehicle, burning off the exhaust and some drips. Because I'm 50 miles from home and had about 2 miles to go to work, I decided to go ahead and see if I could get it to work. If there is something catastrophic, I can leave it parked there for awhile. Oil pressure seemed fine, no knocking, transmission wasn't slipping. At the time I was wondering if it was coming from the transfer case.

I got to work and as I was pulling into park it was grinding and definitely beginning to bind up. My closer inspection at this time found the rear diff plug was gone. I didn't know while inspecting that this is a piece of rubber(?!?!), so I'm trying to figure out how this thing got unscrewed and fell out! It was still very, very hot so I didn't mess with it anymore.

I grabbed some gloves a bit ago (work in a medical type place) and went out and stuck my finger in the diff. It still has some fluid remaining, so I'm really hoping the diff is going to be able to recover after I get some fluid added. It was definitely hot, but still turning when I parked it. Of course there are no replacement plugs in Hutchinson, KS so I'm having to pay same day freight to get one from a Jeep dealer in Wichita sent over to the dealer here.

I'll also check the front diff before driving home as well.

I know this Jeep hasn't been driven hardly at all in quite some time. Is it possible that plug just got hard and shrank some and when things heated up from me driving it farther than it's been driven in a very long time it just popped out? Who thought a rubber plug was a good idea? Is this something I need to worry about? Do people tap these things and put in a screw-in plug?

Thank you, happy Monday. This is not an April Fool thingy.

 

[reece146]

Replace the plug with a metal one.

If there's oil in the case still it's likely fine.

If you think the 'case is not shifting out of 4x4 then verify that the case is getting shifted to the proper positions from under the Jeep. You'll likely have to disassemble the shifter where it attaches to the 'case and futz with it a bit to ensure the shifter goes through the entire range of motion that the case needs.

The Jeep 4.0 is a bulletproof tractor engine but it can have lots of oil leaks. Rear main seal, distributor seal, and valve cover gasket are the usual suspects.

The 4.0/NV242 Jeep is a sweet spot of sorts for Grands. Purely mechanical transfer case behind a bulletproof engine that is capable of better MPGs when driven sanely. It's a "preferred" set up in my mind.

Good luck.

 

[Chi-Town]

If it has a Dana 35 rear diff it will be a simple push in rubber plug and you won't be able to replace it with a metal one unless you swap out to an aftermarket cover. Unless it was damaged last time the fluid was changed the only thing I can think of that would cause it to pop out would be a clogged vent tube.

As for it always being stuck in 4wd, make sure all 4 tires are the same diameter and tire pressure. If one tire is a different diameter it can cause an issue with engagement and disengagement. Also check the fluid level and type in the transfer case. It should be Dexron/Mercon II or III.

 

[DarinM]

Thanks, y'all.
I'll check the vent tube. The tires are all the same, checked the pressure yesterday - passenger rear has a slow leak, so I'll have to stay on top of that. I'll check the linkage and all the fluids and since this thing has been sitting, maybe I'll just park it for a few days and switch them all out this weekend.
A replacement cover might not be a bad idea. It's an easy swap and I'd feel better about not having a rubber plug.

My previous Jeeps have been a CJ5, a YJ and I presently have an '04 Rubicon. I know the I6 pretty well and I'm comfortable with moderate repairs. There are some things I just don't know about/haven't encountered before - and this is one of them.

 

[Chi-Town]

I have a G/2 Cover sitting in my garage for my 8.25 because my rubber plug leaks all the time.

 

[DarinM]

I got the part and a couple quarts of diff lube. Filled it, drove it around the block and then checked the level again. Added a bit more. I couldn't get the front diff plug to budge. Of course the fact that I was lying in a puddle of ice water with sleet falling on me may have contributed to my failure. I'll put it up on ramps where I can get more leverage this weekend.

I had no problems on the drive home. I stopped a couple times to make sure the plug was still in.

Also, it appears to have decided to go into 2wd. I will be checking/changing fluids this weekend and also the linkage as previously stated. It really runs well going down the road. I think I'm going to like this Jeep. It's certainly much more refined than my TJ.

Thanks again for the advice and education.

Y'all have a great day.

 

[d67u57]

as mentioned,you have got yourself a nice reliable truck. 99 or 2000 is when the dreaded head issues started.

its possible that you need to look at the transfer case. chain driven so not much to go wrong but checking(and looking at the state/amount of lube)

is recommended.also if it was left in 4wd forever,sticking can happen. ive seen it on my 93 xj,hard time to put in full time from driving all summer in 2dw.

 

[1stDeuce]

Sounds like you have a good jeep! I have a 242 T-case in my XJ, and I had one in my TJ as well. That case does have problems shifting to 2wd. It likes to stick in "part time" mode, which causes bind. I have pretty good luck turning slightly and then going forward and backward a few times until I don't feel it bind anymore. If I'm going down the road, then I blip the throttle (accel to decel) several times to "shake" it out of 4wd. Any binding will cause it to stick in 4wd, and there's only internal spring force trying to disengage it. I have the fortune of my XJ actually knowing that it's in "part time" thanks to the light. Later vehicles really only lit the light to tell you what mode the lever was in, which is useless.
Chris

 

[DarinM]

Good to know, thanks. I have no light at all working on this one - another thing to track down and fix.
So far it's been running well. We like it!

 

[DarinM]

So we've been driving this thing pretty regularly. My wife is using it as her DD and I've driven it once to work (110 or so miles roundtrip).

It has continued to be about 80% dependable and 20% serious PITA. Some days it runs great, with no issues. Other days it dies at idle, dies going down the road, dies driving through parking lots... It seemed that getting it up to operating temp then parking for a bit (like grocery shopping) and then trying to drive home made it worse. But not always.

I found only minor vacuum leaks; repaired. Just kinda baffled.

Then I found a strange fix on a forum. And when I searched again I found it listed in multiple places, with lots of people saying it worked.

There are 2 screws below the connectors on the PCM. What I found was instructions to back these screws out, and either replace them with shorter screws or put them back in with washers under them.

Now, why would this work? I don't know, but I decided to try it this morning.

I replaced the screws with washers in place and hooked everything back up. Started it up and it coughed and choked a bit. Then it evened out and purred like a kitty. I drove it around the block and it seemed to run really well. Really smooth power band, etc. I got it warmed up and then got my wife to drive it since she's more familiar with it.

We drove around for about half an hour and it ran great. She says it feels smoother, more powerful, idles better.

So we'll see how the next few days go. It's gonna blow my mind if this is a fix that works long term. More to follow!

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[DarinM]

Almost 2 weeks since I did the "repair" mentioned above. Other than one pretty major hiccup that occurred during a deluge of rainfall, the Jeep has been running excellently. We have had no stalling, no burping or farting, zero problems. I think the one hiccup mentioned is due to a poor connection in one of the three plugs going into the PCM. I will be revisiting those with some connection cleaner and perhaps little bungees to keep them well sealed.

If problems do return, I have a friend with a '94 GC that's presently sitting idle. I'll borrow the PCM from his (easy to do with pre-98 models - no reflash required) and see if that makes any difference. But I'm feeling pretty confident that our old free Jeep is much happier than it's been in a long time. And I'm happy because I didn't have to pay the dealership the couple grand they were quoting my in-laws to get it running right!

Happy Friday people!

 

[OverlandZJ]

Your buddy's 94 PCM is not compatible with your 97, OBDI and OBDII.

 

[OverlandZJ]

Darrin, if you haven't yet.. take some time and read over this thread.

http://www.jeepforum.com/forum/f13/12-things-you-can-do-when-your-zj-stalls-1407423/

 

[DarinM]

Thanks, I'll look that over. Good to know about the PCM as well.

 

[yossarian19]

Factory screws were too long so they bottomed out before the PCM connection was tight. Loose connection equals drama

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