Stiff 4WD

[viennatech]

I have a 1995 Grand Cherokee that seems to be engaging the 4WD correctly however there is something amiss.

If I'm traveling at say 15 km/h and I engage the 4PT or 4FT in gravel here is what happens.

Rolling at a slow speed i move the tranny to N then pull up on the t-case handle to 4FT. The console claims FULL TIME and then i hear a good thunk/bang. From there I pop the tranny back into D and drive. Immediately i notice that the engine is now lugging harshly and it feels as if the truck is pulling a lead sled. I can drive, the wheels are obviously working however it is just really stiff. Moving the t case back to 2WD will not disengage the 4wd. Turning corners will make the jeep wobble and the front wheels will protest. If i move to pavement they basically drive along squeeling the whole way. as if i was in a locked 4lo when i'm really in 4hi.

To disengage I need to put the jeep in reverse, then it will clunk and all is well.

I have not been playing much with the system now because i don't want to break anything befdore checking this out.

I also noticed that if i do mess around, for the next day or so i will get mad clicking at any speed coming form the front end. After about 1000 kms or so it goes away. perhaps this issomething to do with the way the front wheels lock up? \

Forgive my ignorance as i'm coming from cars and this is my first real vehicle! No owners manual was provided however i'm pretty well inclined mechanically and so i have a good understanding of what's happeneing, just now whether this is a jeep thing or not.

Thanks all!

 

[DaveD912]

I'm also new to Jeeps, but not 4wds. When you go into FullTime, the transfer case changes your gear ratio - I think that's what you're feeling. The recommended way to get in and out of Fulltime is to have the tranny in neutral and be rolling slowly (I've always rolled a bit under 5mph). You should not need to go into reverse. I've noticed it sometimes takes a while for my 4wd light to go out - just figured it was normal since my Dodge Ram did the same thing.

 

[dmillion]

Okay, first off, on all Jeeps, the transfer case does not change your final gear ratio unless you put it into 4-lo. In 4-hi the transfer case's gear ratio is 1:1. Second, you do not have to slow down or shift into neutral in order to engage either 4-hi-pt or 4-hi-ft. The transfer cases in Jeeps are "shift on the fly," which means that at any reasonable speed (Jeep says up to 50 mph) you just grab the handle and yank it into 4-hi.

Beyond that, I have no idea why you are getting the symptoms you are, viennatech. Does the Jeep have any other modifications that might affect this?

 

[viennatech]

The Jeep is bone stock. Since it's a ZJ I assume that the previous owner likely never put it in 4WD , ever.... So maybe soemthing is tight or rusted or?

I am afraid of breaking something by just driving it when it's in 4wd and i don't have any friends that drive a cherokee so i can't compare what is "normal" versus what i have.

I can say that it sure makes a difference when i shift it in. you can tell that the driveline is trying to blow itself up.... I just don't know where to look to test/repair.

Any other thoughts?

 

[Speed_racer]

Try nagca.com

that doesnt sound normal.

SOunds like time for a rebuild to me.

 

[viennatech]

After reading a lot of great posts I think that part of my problem is attributed to 4x4 "wind up" I realized yesterday that the tires on this jeep are mismatched. I have 235 75R15 on the front but 235 20R15 on the rear. I realize this is a slight difference but would it easily be enough to wind up the drivetrain?

I'm going to go ahead and get a set of new tires all around before i continue on my quest for off road thunder.

 

[DaveD912]

My bad. This thread was originally in the XJ forum, so I (incorrectly) assumed you had a 231 xfer case like mine.

dmillion - doesn't the 231 have 2.72:1 in 4lo?

 

[viennatech]

If I don't have a 231 what would it be? i have a lever on the floor with 2wd, 4pt, 4ft , n, then 4lo.

I believe they call it "selec trac"

 

[dmillion]

Yes, in 4-lo all Jeep transfer cases lower the gear ratio. The second posting above says "When you go into FullTime, the transfer case changes your gear ratio." That is not correct. The FullTime (4-FT) position is a "high range" with no lowering of the gear ratio.

If you have the transfer case in the 4-FT position the front and rear wheels will be able to differentiate some and the small difference in tire size should not cause binding. If the transfer case is in 4-PT then that is different, no differentiation between front and rear is possible, and binding could occur.

It sounds like something is wrong and you need to get this looked at. I would advise, like someone else said before, that you check in with the NAGCA forums. You'll find a lot more Grand Cherokee expertise there, as this forum is dedicated to the "other" Cherokee--the XJ. Don't know the URL, but I'm sure you can find it through Google or whatever.

Good luck.

 

[Rob Mayercik]

If I don't have a 231 what would it be? i have a lever on the floor with 2wd, 4pt, 4ft , n, then 4lo.

I believe they call it "selec trac"

That is Selec-Trac, which is also referred to as the "242" t-case. This was offered as an option on some XJs

The "231" is the Command-Trac case, which I think was never offered on ZJs. It was, however, standard on XJs, and the only option for XJs with manual transmissions.

If you're absolutely sure you're in 4-Full Time when you experience the "windup", the first thing to do (after getting it back into 2wd) should be to check the adjustment of the transfer case linkage. If it's out of adjustment, you may not be in the mode the lever indicates. Try that before spending on new tires - I agree with Don that a small difference in tire size should be no problem for a properly operating 242 in full-time mode. You can always reshoe after checking the linkage.

Owner's manuals should be relatively cheap from Chrysler (about 10 bucks), but here are the basics for the 242 tcase:

2Hi : 2wd, high range. Normal mode for most driving conditions.

4Hi : Part-time 4wd, high range. NOT to be used on dry pavement. Center diff (in case) is locked, causing both driveshafts to turn as one.

4FT : Full-time 4wd (sometimes called AWD). Center diff is unlocked, which is why this mode is safe for use on all surfaces.

N : Neutral. Self-explanatory.

4Lo : Part-time 4wd, low range. Engages gear reduction (2.72:1) inside case. Center diff is locked, so like 4Hi, you cannot use this on dry pavement.


Rob

 

[viennatech]

Thank you Rob for your clarification of the t case and it's operation. I too had thought that the 4FT setting should not lock up the way it does.

If this is a metter of t case linkage adjustment could i then in theory play with the lever, say pull it past 4FT almost to neutral and see if i feel a shift in behaviour or is there a more scientific method of checking this linkage.

I am looking into joining a local jeep club to be able to at least see what other's jeeps are like and how they act.

I have been checking on the other board however i find this interface seems much cleaner and you all seem very knowledgeable in the XJ/ZJ's.

Is a ZJ not mechanically the same as an XJ? i mean i understand it has more bells and whistles and leather (who ever thought a 4x4 needed leather!!) But all in all does the advice for one not apply directly to the other?

Thanks again for the great insights!

 

[Rob Mayercik]

Thank you Rob for your clarification of the t case and it's operation. I too had thought that the 4FT setting should not lock up the way it does.

If this is a metter of t case linkage adjustment could i then in theory play with the lever, say pull it past 4FT almost to neutral and see if i feel a shift in behaviour or is there a more scientific method of checking this linkage.

No problem. I don't know a whole lot about adjusting the linkage, other than suggesting you find a repair manual and see how it says to do it. Local libraries might have a Chilton's or Haynes' to get you started, but if you're planning on keeping this vehicle a while, call Chrysler and get a Factory Service Manual (FSM).

Never having played with the tcase in a ZJ, I don't know if your idea will work, but that might be a way to start.

I am looking into joining a local jeep club to be able to at least see what other's jeeps are like and how they act.

I have been checking on the other board however i find this interface seems much cleaner and you all seem very knowledgeable in the XJ/ZJ's.

I've found this to be about the best place for XJ info - the knowledge base here is truly staggering at times.

Also, have you looked into the Grand Cherokee forum over at Jeeps Unlimited (http://www.jeepsunlimited.com)? Also known as JU for short, it's sometimes a bit more rowdy (and sometimes they seem to make silly suggestions), but it might be worth searching there for a linkage adjustment procedure. You never know when you'll find a diamond in the rough.

Is a ZJ not mechanically the same as an XJ? i mean i understand it has more bells and whistles and leather (who ever thought a 4x4 needed leather!!) But all in all does the advice for one not apply directly to the other?

Thanks again for the great insights!

Some things are similar - since you've got the 242 tcase, you've also got the 4.0L engine and (I think) the AW4 automatic. Both of these are common in XJs, though there may be some slight differences in the 4.0s from XJ to ZJ. Beyond that, it's pretty much hit or miss. I will have to say though, that considering the range of axles people here have been through it's unlikely that your ZJ will have an axle under it that nobody here has seen or run.

Good luck,

Rob