I appear to have an number of drive train related issues happening, but I am going to start with the most disturbing symptom first.
I have a 1999 Jeep Grand Cherokee Laredo 4WD with a 6 cylinder engine. I’ve got just under 100K miles on the Jeep and it has been fairly well maintained.
I topped off the transfer case with Mopar ATF-4 Synthetic, which I was told by the dealer is what they use (The manual recommends Dextron III). I rarely use the 4WD, but I decided to run the transfer case thru all the settings just to make sure that the lube got everywhere.
When I made a tight turn in a cul de sac while in 4WD, I suddenly felt a drag on the wheel as if the front tire were dragging. It was not. The turn actually made the rear wheels chirp as well. Switching to 2WD didn’t immediately alleviate the problem. However, after shifting back and forth a few times the “dragging” problem went away. This is scary, because if the wheels ever did this kind of lockup at speed I might severely damage something or lose control.
Might this be caused by the Transfer case? I would have thought that it might be the front differential, but when the back wheels locked up and chirped it would seem to eliminate this as an option.
Now for full disclosure. I just changed the gear oil in both the front and rear differentials with SAE 80-90, which is what the manual and the dealer recommend. The fluid from the front was clear after 30K miles, like it was brand new. The fluid from the rear was dark, but not burned. Both diffs were filled to the top of the drain hole.
Also, the Transfer case is leaking. I keep it topped off, but before I realized that I had a leak, it had run dry at one point.
So, what motivated me to start messing around in the first place was that I have a “shoop-shoop” sound coming from the general area of the transmission. At first, I thought that I had a bad wheel bearing because that was what it sounded like. Then I noticed that the sound happens in Neutral and Park. I’m hoping that if I have a problem, it’s confined to the transfer case since I am going to have to have the mechanic pull it apart to fix the gasket anyway.
The transmission seems to be fine. The fluid is clear and at the correct level.
Any suggestions or ideas? How dangerous is this situation?
Thanks.
When it did the herky jerky, was it in full time or part time AWD? In part time, which is designed to only be used PART TIME to get you out of a ditch, it will do that every time.
Don’t use 4WD on dry or wet pavement. Use it in dirt, mud, gravel, snow, ice, snow on road or ice on road. Always check for loose lug nuts after a day of off road 4WD.
It will take a little driving out of 4WD to get it to unbind if you turn corners under good driving conditions on paved roads.
What you describe is perfectly normal behavior for any 4-WD vehicle. When you shift the T-case into 4wd, both front and rear axles are locked together mechanically. When you turn, your rear wheels do not track directly behind your front wheels. So they must rotate a slightly different speeds. But they can’t because they are locked together. So they bind up and SOMETHING has to give.
All Wheel Drive vehicles add some sort of differential or viscous coupling to the transfer case to accommodate this effect. These systems are not known for being trouble-free.
As you have just learned, shifting a vehicle into 4wd “so it will be safer” can have the exact opposite effect. 4wd has one basic purpose. Getting unstuck when you are stuck. You don’t drive down paved roads in 4wd unless conditions are really, really bad and your speed is limited to 35 mph or less…
If you did this on DRY pavement…then it’s WORKING perfectly…and I suggest you NEVER do it again. Great way to lock up a transfer case or even completely destroy it.
Thank you, everyone, for your responses. It is reassuring to know that what I experienced was normal. It’s also nice to know about the whole “never on dry pavement” thing. I’ll NEVER do it again!
So, now I want more…
Does anyone have ideas about what the “shoop, shoop” sound might be? Hopefully something external, like a drive shaft, and not something internal, like a bearing in the transmission!
Thank you all again very much!
If “shoop-shoop” happens in “Park”, NOTHING is turning past the torque converter and front pump in the transmission. Up on a lift with the engine running, it should be very easy to isolate…
“Never on dry pavement” is not always correct for Jeeps. what matters is what Transfer case you have for this to be true. Do you have a selector that says 2HI, 4 HI Part Time, 4 HI Full Time, N, 4 LO Part Time (NP/NV 242 Selec Trac)? or is it a 2 HI, 4 HI Part Time, N, 4 LO Part time (NP/NV 231 Command Trac)? if you have Selec Trac you can drive on dry pavement in the 2 HI and 4 HI Full time modes (Per the owners manual). The transfer case has an open diff in the 4 HI full position which allows different drive shaft speeds. 4 HI Part time and LO is a LOCKED transfer case which will give you the bucking on dry pavement and is only meant for loose surfaces.
Also when taking it out of 4 WD it may take some load and unload of the drive train to disengage the 4 WD selector from the shaft, there are many different reasons it happens but nothing to really worry about, if you are stuck in 4 HI and are able to stop and put the Transmission in reverse and back up a couple of feet this will disengage the selector faster and put it back into 2 WD.
Hey its called the “Ackerman Principle” perfectly normal for a normal 4WD SYSTEM with no center differential or means to accomadate the different speeds the wheels will be turning in a turn(the different arcs the wheels run in are different lengths,so the wheels try to turn at unlike speeds-hence the binding,since they are basically coupled together-Kevin
You didn’rt run over Cher, did you? 4WD likes to make more noise than you would like. Mine sounds funny too.