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2000 Jeep Cherokee Classic - Car Jolting?

First…LOVE THE SHOW!!
I have a 2000 Jeep Cherokee Classic with 214,000 miles on it.
Ok…this hasn’t happen too often, but scares the CRAP outta me when it does.
The other day, it happened twice.
Traveling on the highway, 65 - 70 MPH, the car suddenly jolts with a loud BANG!
I’ve had the transmission fluid flushed.
Each time I go in for service at my local garage, I have them check ALL the fluids.
They never find anything. And are at a loss as to what it could be. They’ve dropped the pan and found nothing wrong with the transmission. No metal in the fluid. They’ve check the rear diff. Still nothing.
I’ve gone about a year without the issue until this past Monday when it happened twice.
I’m a little paranoid to go faster than 60 - 65 right now.
Any suggestions?
I need to get another year outta this. At least. I don’t have boat payments, but I have another year of college payments for my daughter.
Oh, and I’m pretty certain I don’t drive like your brother. :slight_smile:

That noise might be caused from a worn front drive axle U-joint. Have those U-joints inspected.

Tester

Won’t it then happen more often?
I have to take it in for an oil change anyway, I’ll have them check that.

It will happen more often if it is a U-joint. The wife had a 99 Cherokee. And that’s how it started out when the front U-joints wore out.

Tester

I don’t know. I’m no mechanic, but this doesn’t make sense. I could see it if it happened in the middle of a turn, but this has happened while always traveling straight.
Vehicle does have 4WD, but that is not engaged when this happens.

Stuff is still turning even whith the 4wd off, so all those joints need to be examined, like Tester said. Also, the vacuum-powered axle disengagement devices might not be working.

What does the vacuum-powered axle disengagement device do? And if it’s not working, what is happening? Is this something I can check myself?

It is on the front axle and it engages and disengages the front wheels from the transfer case. You’ll want to get a Haynes manual to check it out.

But only engages/disengages for 4WD right? Could it be trying to engage/disengage on its own then?

That, or it could be failing to disengage.

If the “bang” happens when you are coasting (no load condition on drive train) then a bad U-Joint or CV joint is a good possible. Slack in the drive shaft(s) allows things to shift around.

There is a “spine” that slides a bit where it connects to the back of the auto trans. Putting some grease on that spine isn’t usually required, but at this age and miles is worth a shot.

There are mounts for the motor, transmission, and axles, so all mounts need to be checked. A bad mount allows things to move more than they should.

If none of the above check out you might have a bad gear (or a going bad gear) internally in the transfer case, front differential, or rear differential. If so, one day the bang will result in that part locking up completely, meaning a pretty dramatic stop if you are going 70 mph on an interstate.

I had a rear end lock up on me in just those circumstances (a bearing seal went bad and all the differential fluid had leaked out) and both rear wheels just locked up and the car was a bear to control and get off the road safely. Once it came to a stop that’s where it stayed until towed. In a long driving career over many miles, this remains one of my top 5 wild moments behind the wheel.

You need to have a real Jeep mechanic, not a lube rack “technician”, go over the entire drive-line, brakes, motor-mounts, everything that moves or can move…

are we assuming its not the beginning of a the death wobble? I had a wrangler that started making a popping sound like that at high speeds, eventually started shaking violently at random times… replaced the track bar, steering stabilizer and tie rod; problem went away…

These all sound like pricing problems…I’ll have them all checked out.

I had a thought…I forgot something that might be related:
What about the drive shaft?
About a year ago or so I was towing a trailer, and could drive faster than say 50. THe car shook. Last time I felt that, it was the U Joint on the drive shaft.
But my mechanic said they were fine.
It wasn’t too long after that that these symptoms starting happening. It only happens every several months, but I suspect at some point will get progressively worse.
Thoughts?

Could be. Have everything checked out.