Annoying Thumping! Any Ideas?

Ever since I bought my XJ a few weeks ago, I've had this annoying thumping that is hard to pinpoint where it's coming from. It appears to do it while in right hand curves, and running about 40-45mph....and recently while driving straight down the road. But the problem is it occurs at any given time and any given place. It almost sounds like square tires, but I had them rotated and balanced and the problem didn't go away. I have noticed that when ever I apply the brakes the thumping seems to go away. I can almost feel it vibrating too...and right now, my best geuss is it is coming from the right front somewhere.

I also have a brake squeel that comes and goes....and I believe my brakes are sticking as I was going through a parking lot the other day at about 5 mph and they were squeeling while I was NOT using them. I quick, and rather hard tap on the brakes stopped this.

If somebody can point me in the right direction of where to start looking, and give me some signs for obvious stuff that is worn or broken (don't know a whole lot about Jeeps, but i'm not a total stranger to them and i'm anxious to learn more). Because if I can find out what it causing this, I still have about 1-1.5 weeks left on my warranty, which would mean more free repairs for me.

If it's under warranty why not just take it to them and tell them to fix it?

Because I don't know whats wrong with it. And this is Carmax, not a Jeep dealer. Plus, that would mean my mom would have to be back in a rental for an unknown time period, and i'd be back in the KJ, and it would be a big inconvenience. If I could get some ideas of where to start looking, that would help alot.

Stuck brake caliper/warped rotor comes to mind. That would be the cheap fix. I'm also thinking worn ball joint or even wheel bearing, but I think I'm missing something before making that diagnosis. Off to find coffee...

Sounds like a wheel u-joint to me. I had one freeze up and gave almost the same symptoms.

I agree with Old_Man. I had the same sound at intermittant times and it ended up being one of my front u-joints. On mine you could see rust all over the u-joint. Take a look at them if they aren't rusty take it to a tire shop and see if they will check them for you free. Les Schwab does. Any of the larger tire shops with brake shops may.

U-joints. Same prob with my 85 and went under and they were loose. Changed them and problem no more.

mmm hmmmmmm. Thanks to all for pointing me in a direction. Once all this ice stuff clears up i'll crawl under and have a look.

I had the same thing. Mine was a loose Brake Caliper. The Caliper bolts were stripped and kept coming loose. I had to Heli-Coil it. Been fine ever since.
But if in fact it is a loose caliper, I'd suggest taking it back to the dealer and telling them to fix it please, as this is a safety issue.

Thats what i was thinking, as it goes away with braking. But the thing is, I had them inspect the brakes last time I brought it in, cause they were squeeling. Of course, I was not there, so I couldn't watch him pull the wheels off, and they said everything just fine. I get the feeling that the brakes were never looked at while they had the wheels off to balance them (they did do that). Perhaps Tuesday when i'm off from work and I can get the Jeep in the garage out of the cold i'll have a peek myself. Thanks to all for the help.



On another note, I am LOVING selec-trac. That full time option came in VERY handy today on the solid ice roads. Saved me from hitting many a street sign and old people driving stupid. Plus the face the main roads were slushy, and the side roads were snowy/icy, ment no shifting between 2wd and 4hi, like on command-trac.

Ok so I'm driving to work tonight, and out of no where, the entire front end starts bounding up and down....like a couple of very square tires. I immediately pulled over and had a look, to find nothing wrong. I'm about a block away from my work at this time, and I call my mom to tell her to make an appointment at Carmax for tomorrow morning, first thing. I get back in, and get back on the road and everything is fine. BUT (there's always a but), as I'm pulling into the lot (which starts off going down hill with a mild bump), the minute I hit that bump I heard this god aweful scraping noise (the wheel is halfway to full lock). As i straighten out the wheel, it goes away. I then pull into a section of nothing but empty lots, in an attempt to create the noise again. Sure enough, same metal on metal....almost steel on steel.....this isn't like fried brakes scraping.

First thing that pops to mind is Right front U-joint. When I got to work I grabbed a flashlight and looked closer to see that the right one is sort of rusted, and the left one is on it's way to being like the right one. And tonight, it didn't grind, but it did thump, and now it's pulling to the right really bad. My warranty runs out in 3 days, and I had to demand an appointment w/ carmax for tomorrow (they tried to push it out 3 days to say that it's out of warranty), so I have a few Questions.

Am I right in saying the U-joint is going bad?

About how much would it cost to replace it if I did it my self (thinking of in the future when the others go)?

It looks very easy to get to (I do have access to a lift at a buddies shop), is this a hard job to do?

What is the average life of the U-joints? From the reviews I've read on various sites, it seems to be a common wear and tear part on Jeeps.

Could this be the cause of my rapidly falling gas milage?

Having it start when you hit a bump is not indicative of a bad u-joint, but more like death wobble. The screech sounds like a U-joint.

DW can be caused by any loose or worn joint in the front end. A search will flood you with info on curing the DW's.

The death wobble started out of nowhere. And was much worse than the mild thumping that had been occuring recently.

Intresting people they are down at Carmax.

I skipped school today to go have my Jeep looked at (my mom took the morning off since it's in her name). I got down there, and they said, If you don't mind waiting an hour, we'll get it up on the lift and have a look and see (keep in mind the thumping, grinding, and severe pulling to the right i've had lately). The mechanic got it up on the lift, ran it through 4X4 and did some "tests" to see if he could hear or see anything out of place. We then went on a long test drive to see if i could duplicate the problem with the thumping. Of course, it acted like a perfect Jeep...not one peep out of it, except for the annoying brakes. So as we're driving around, here's what the mechanic tells me, personally (real nice guy). "While I had it on the lift doing some tests, I noticed the brakes suqeeling very badly. I also noticed this was mentioned the last time you were here, and a record was made on your account about it. I know they told you the brakes are fine, but I really think they need to be replaced. I know chrysler had a TSB out to replace the calipers, rotors, and pads on the late 90's Jeeps. When we get back i'll do some research to find those TSB's, and see if it applies to the Cherokee. I also noticed some binding in the U-joint while in right turns. If it were my choice, I would replace all the brakes with upgraded materials, and throw a new u-joint on there, for peace of mind. But it's not my choice, I have to run everything by my service manager first"

When we got back, they took it back and put it up on the lift again, and had a much closer inspection, and noticed the aftermarket shocks (nascar shocks, put on by the previous owner), the right front was bent, and was rubbing against something. They didn't know what, but the shocks are tan in color, and it has been rubbing against something black for long enough, that it's rubber through the paint, down to the metal of the shock.

So to sum things up, I am now getting a new set of shocks (all around), they're going to spray some more anti-suqeel shtuff in the brakes to shut them up, and I noted, as well as the mechanic noted, that the steering wheel has to be turned to the left notceably in order for the Jeep to drive straight. So it needs an alignment. This should all be FREE, as my warranty runs out tomorrow.

Perhaps this weekend, if I can get my buddies shop for a couple of hours, I'll put it up on a lift and have my dad look at it with me. I did manage to get a decent look at the rest of the underneath while it was up, and I didn't notice anything out of the normal for any car (no holes in stuff ther there shouldn't be any, no leaks, that kind of stuff).

Thats whats going on so far. I'm open to suggestions and comments from anybody as to where I should go from here, once my warranty is up and i'm on my own for repairs. I am not sure what type of shocks are going on here. They said they would try to get OEM if possible, but, we are all trying to have it back in my driveway by tonight, since this is my only day off from work this week.

Thanks to all for the input, and I look forward to more.