I recently bought a 2000 jeep cherokee XJ. It had some known issues which i was fine with but turned out to have a lot more issues than i was expecting. It sucks because i have a very tight budget and was not expecting to have to do so much work to it. But its a little to late for that now. So i have been going through and fixing everything that needs to be fixed. Most of the issues are fairly easy fixes like a broken window, broken latch handle, new struts for rear lift gate, no air filter, coolant change, oil change, blower motor fan not blowing. I have prioritized the things that are essential for the cars function as i just need a drivable vehicle and can fix the other stuff as i go. Ive done a few cosmetic/non essential things while waiting for parts to come in as i can find them cheaper online than locally and i also only have a motorcycle and cant carry much so having them delivered is convenient.

So far the essential things I've done have been changing the oil, putting in a air filter as it didn't have one, the TV cable was frayed and hanging on by a thread so i had to replace that. to replace that i had to get inside the transmission so while in there i replaced the transmission filter and changed the oil. I had death wobble and narrowed it down to a loose track bar. I went to a friends shop and he helped me installing a new one. Turns out whoever put in the old one cross threaded the bolt and completely destroyed the threads on both the blot and the nut so it wasn't able to be tightened. once i left my friends place to head back home i noticed a check engine light came on. surprisingly with everything that seems to be wrong with the jeep the light had not already been on. but i drove the jeep home (about a 30 min drive) with no issues. I took the interstate to get some speed to test if there was any death wobble still. none. seems as though thats fixed.

however when i left this morning to grab some grease for the new track bar, didn't have any last night and was too late to buy any at the store, on the way back to my house which is less than 2 miles round trip i started to get a vibration around 40MPH. this wasn't anything like the previous death wobble i had before the new track bar. it was a vibration/ light shaking. i greased the track bar then went out agin for a test drive and got up to 40MPH and started to feel the shake again. i turned around and went back home. going down the hill on the road near the house i slowed down and i heard a steady thumping sound. the sound seemed to increase and decrease along with the speed i was traveling. i also put my hand on the center floor wall right below where the center dash meets the carpet and could physically feel the thumping. At first thought with the sound and feeling i thought something was wrapped around the drive shaft and was slapping the underside of the jeep. i got home and got under neath the jeep and checked and nothing. i grabbed the drive shaft and shook it to see if it was loose of if the U joint was loose where it connects to the transmission and it was fine. i jacked up the front and checked the front end stuff to see if maybe the death wobble was back in a new way and it all seemed fine. moved the tires to see about the wheel bearings being the issue and everything seemed to check out.

Now i am pretty mechanically inclined and have always done my own work when at all possible. i need to do my own work now too as i don't have the money to pay someone else to do it. That being said i have only had a Motorcycle as my transportation for the past 10 years or so. Because of this i haven't worked too much on cars and don't know what else to look for or what is normal or acceptable on a car. theres a lot more than a motorcycle.

while searching for potential solutions with no luck i was able to find out that you can pull your own check engine light codes on the jeep without using an OBD2 reader. I tried this in hopes it would show a code related to the issue. no such luck as even though my check engine light is on it did not show any codes. from what i saw online you turn the key on 3 times and on the third time keep it on and it shows the codes. it did not do anything.

Im wondering if anyone has had this same issue and what you did to fix it or am looking for suggestions on things i can check and test to diagnose the issue. Any suggestions and help would be greatly appreciated.

 

As you said you could feel it like it was hitting the floor, the first thing I'd suggest is to take a good look underneath.

Look around the propshafts for any clearance issues, check your engine and transmission mounts. Check the exhaust mounts haven't popped out or snapped.

 

get an obd2 reader, so cheap, or borrow one and read any stored codes

have a look at the torque convertor bolts is what I would do first

whatever is thumping as you described is probably rotating ?

 

I had my dad come over to get another pair of eyes on it. He knows a lot more about cars than i do. the only thing we were able to find that might be the issue was the output shaft of the transmission had a good bit of play in it. the seal was also leaking a bit. We took it for a test drive to so he could hear what it was doing and had no vibration or sound at all. no issues. maybe messing with the output shaft put it back into a good position and didn't vibrate due to that. Either way i need to fix that so that will be my next step.

I will give updates once thats replaced on wether or not it fixed the issue.

 

My 98 2WD Classic had a vibration from the prop shaft, and the seal was also leaking. The 2WD transmission extension housing contains the shaft seal and the bronze bushing immediately in front of it. When the seal begins to leak it's a sure sign of the bushing being worn over-size. That bushing holds the prop shaft spinning true and when it wears run-out occurs (wobble) that quickly takes out the seal. A new seal won't fix it. There is no replacement bushing made for that extension housing. The design, goofy as it is, calls for replacing the entire extension housing when the bushing goes. Mine did but instead of replacing the housing I pressed out the bushing, brazed in new material, opened up the ID on a lathe, cut new oil lubrication channels with a Dremel and burr, pressed it back in and honed it to fit the prop shaft. If I remember correctly, the tolerances in the maintenance manual state that .003" clearance between the shaft and bushing is the maximum wear allowed on the bushing inner diameter. Mine was somewhere around .006" clearance. After I was done I had .001" clearance. All that said, the wobble and vibration wasn't like something was significantly out. I would think that the transmission mount might have failed to cause the kind of vibration you describe. If you grabbed the prop shaft and gave it a good shake you might have unwittingly re-aligned the transmission (temporarily) and trued it back up.

 

So I ended up getting the new bushing and seal replaced. Got the new bushing and seal both for about $6. Wasn't too hard to replace it all either. I took off the extension housing then drove out the old bushing with a socket, breaker bar, and a hammer and drove the new one in the same way. I have not had anymore issues with the vibrating like i did before so hopefully that was the issue. If it comes back then ill update this thread but hopefully i don't have to. Thanks again for the suggestions and help.