Thump in rear... what IS that???

I have a 2004 Liberty Sport 4x4 with 6 cyl. engine and auto transmission. Since new, it sometimes does this thunk when coming to a stop and downshifting into first, kinda like something just kicked it in the rear. I took it to dealer who said that it is a "normal quirk" in the Liberty and many Chrysler products. I now have 43,000 miles on it and now... but only once in a while... when starting from a stop with engine warm, like sitting in traffic, I give it gas and it thumps forward like someone rear-ended me, but no one did. Not sure if the brakes may be sticking and suddenly unstick with that thump or does this sound more like transmission woes? I luckily have the 7 yr/70,000 mile powertrain warranty, but don't want to hear "that's normal" from dealer. Anyone else have this? If so, what did you find caused it? It only happens maybe once a week, so to recreate it for mechanic is near impossible.

I spoke to the Jeep dealer service advisor today and was told that unless the warning light is on, allowing them to read the error codes (which it is NOT) or the mechanics can reproduce the "thump" (which only happens occassionally... not at all today!), there's nothing they can do. I'm wondering... does this sound like something serious lining up, like now is a good time to trade in while it's usually running fine... or is this just a quirk of an aging Jeep (though 43,000 miles is far from "old"!)? I like the vehicle a lot otherwise. Did great recently in very windy, rainy weather with flooded streets and slippery conditions in 4WD. Hate to trade and take a hit if this problem may be just something minor... dealer of course would say, TRADE to new one! Any recommendations?

its a jeep thing you wouldn't understand (lol)any way a thump in the rear do you hear it over bumps probley would have to hit the bump pretty hard, may be rear upper control arm bushings and or the ball joint that mounts on the rear dif and to the rear upper control arm. i have replaced a few of them on libertys. any other info you have on what makes the noise or causes it could help fix this thing i will check on any tsb's for your problem

there is a flash up date for harsh engaugement make sure your pcm is up to date. also found a str online recomendation fo rear drive shaft dampning but chrysler dont have a fix the say to send the drive shaft to a person that specializes in driveshafts

It doesn't happen over bumps... just going on level pavement, it seems to thump when either shifting down into 1st gear, coming to a stop or when starting out from a stop in 1st. Wayne069, thank you for looking up possible issues... could you post a link to where these updates are that I could print out and bring to the dealer? Alas, I am not very mechanically inclined (I can, however, change an air filter on my own LOL!), so what is this about drive shaft dampening? I saw in Consumers Reports the real trouble spot being driveline... don't even know what that means. Yet the transmission came out better than average regarding major repairs... would a drive shaft problem make that thunk? It only happens once in a while... like 1 or 2 x a week. But it is shocking and feels like the person behind you hit you. Otherwise, I love my Liberty... very dependable and has gotten me thru Fay (I live in Florida) with her winds and flood waters. By the way, it shifts smoothly in and out of 4WD... no noises or anything.

I have this same EXACT problem with my my 2003 Liberty. It's annoying as heck. I've thought about checking the ball joint on the top of the rear axle, but wasn't really sure how to.

Any advice?

BTW, my Jeep has 79,000 miles on it.

ShafferNY, belive me, I FEEL your pain! I too have been to dealers (two of them) one when I only had a few thousand miles on it and they said it's "a Liberty thing" and not to worry about it. That did not make me happy, but I tolerated it as it happened very infrequently. Now, with 43,000 miles, it is not only thunking in the rear when I slow to a stop (shifting down into 1st gear), but now it sometimes does that when launching after a stop (again in 1st gear). The first dealer said they could not do anything with it unless they could re-create the problem (sound familiar!?). Or, if the check engine light was on, then they could read the codes, but the light never went on. The second dealer said their tech would look at it as I asked if it could be a computer update that was needed. He said perhaps, or it could be something else, that he would check it out... for $100!!! It has the 7 yr./70,000 powertrain warranty and come heck or high water, that dealership WOULD get that deductible! So, I left and went to AAMCO (the transmission people) and talked to the manager. He said the 2004 had the OLD Chrysler 4-spd. auto. and they didn't put in a new version till 2005. He said there are NO UPDATES for the 2004 tranny and the TSB's did not apply (no engine light on). He recommended two things:
1. drive it until it is doing the banging in the rear often enough for a dealer's service person to experience it, then have them repair or replace the transmission under warranty. (He thought it would get worse in time).
2. if it still was intermittant, then before the powertrain warranty expires, GET RID OF IT.

I'm so pissed... otherwise, I love the little Jeep. Need to hear from owners who have resolved the problem and how they did it. By the way, the ball joints were replaced under recall, so should be o.k. And this only happens when in first gear, so figured it was transmission. HELP fellow Liberty owners!!!!!:crying:

I recently had a problem with both rear calipers sticking. So I replaced both rear calipers and put new shoes on before taking a 200 mile trip to New Hampshire last weekend. During the road trip it would still do it intermittantly. At this point I've ruled out a sticky caliper causing this.

My other thoughts are:

1) Driveline slack - This could be due to worn driveshaft u-joints, excess play in the rear end gears, or a stretched chain in the transfer case.

I used to have an old Chevy truck with New Process 203 transfer case which is a chain drive transfer case and it would clunk a bit when you put it into, or out of gear. My jeep does not do this however.

2) Worn rear ball joint on top of the rear axle. I haven't figured out a good way to check this ball joint assembled, so I may have to unbolt it to check for looseness/play.

3) Bad tranmission/transfer case mount. I haven't even looked to see how the mount is set up or if this could even be a possibility.

These are some things I'm going to look at before the snow flies.

Well the old (45RFE) Chrysler tranny in the liberty's were changed in the middle of the 2003 year. If you have a 2004, I would assume you have the new tranny (42RLE).

See this site: http://en.wikibooks.org/wiki/Jeep_Liberty/Transmissions

I have a 2005 with the new tranny and have a somewhat similar problem. Only when the jeep rests for 6-8 hours it "thumps" the first time I put it in drive.

I mentioned this to a dealer and they said that it can take 3-5 seconds for the tranny to shift into drive, and the thumping didnt seem to be an issue.

Wonder if this issue is related....

Well either way, the dealer probably told you wrong and you should see if an update is available for your computer (I need to do the same thing).

Good luck.

http://www.jeepkj.com/forum/showthread.php?t=35672

Interesting.

I have a 2005 Liberty Renegade that makes an awful noise in the rear when backing up, not all the time but often. It does it going forward aswell but isn't as noticable because the forward speed is faster. Dealer heard the noise said the caliper was hanging up, put new calipers, rotors and pads in it and it just did it again tonight.

FYI...A couple months ago I had my transmission flushed and flashed at a Jeep dealership. I haven't had a problem since then. In fact, I had forgotten about this issue alltogether until I came back across this topic.

Shaffer, is that the first tranny service you had done on your Jeep? Wondering if I can wait a while on mine, have about 63,000 miles.

It had 74000 miles on the jeep when I bought it. I got it in for a flush as soon as I afford the $300 for it.

My '03 has a 45rfe transmission and there is a tsb regarding a transmission fluid change. Once all the fluid is drained from the transmission, the 45rfe likes to act funny when refilled. As a result the dealer usually does a "quick learn". I think this quick learn is what fixes the transmission shifting. Could be the new filters too.

Chrysler transmission need to be servided every 40k if they are not the transmission will have a tendacy to have sticcking valves which cause many problems, the most comon is harsh downshift, the transmission should freewheel while slowing. I would service the unit and add lucass to free the valves and solenoids. All the cars with this problem that I have serviced this way gave positive results.

Good luck with your Liberty's....sold ours recently. Wife wanted something a little more comfortable to drive around.

Sounds like what my Chrysler dealer called a "bump stop" in my '00 Caravan. It got pretty bad, thought for sure I'd been rear ended a few times. They put some electronic box on it & it went away.

I bought my daughter a 2004 Liberty. The vehicle was priced well but was accompanied with a thump in the rear. I identified the problem and had it fixed. The issue was the rear upper control arm ball joint... The trick is, it's not the ball joint or the control arm that is bad. The problem is the mounting bracket that is bolted to the top of the rear end differential. The bracket gets tightened around the ball joint and secures it. The problem comes from play developing and over time it hallows out the bracket and if bad enough the ball joint can come completely free of the bracket. This causes the differential to be able to rotate forward and back until it finds something to stop it with a "thump". The rear lower control arms were recalled recently due to a safety issue. I have found information that this problem is very common but no accidents have been caused due to the problem so they are not doing a safety recall. Way to go Chrysler! I hope my post helps someone. The dealership would have never figured it out, I had to find it myself.