Slow speed klunk starting and stopping

GordnadoCRD · **Posted:** Mon Jul 31, 2017 8:47 pm

L27 / L27R Recall for Rear Lower Control Arm corrosion / breakage issue.

mrhemi · **Joined:** Tue Dec 08, 2015 10:46 am **Posts:** 180

https://www.mopar.com/jeep/en-us/my-veh ... calls.html

Type your VIN into the website link. It will tell you what recalls are applicable to your vehicle and if they have been completed.

Steve777 · **Joined:** Fri Oct 16, 2015 11:31 pm **Posts:** 279

Well I am back to looking for the source of this clunk. Did some reading online, thinking about the symptoms (always dangerous I know :lol:

), and a little crawling underneath. Have not taped a camera under it to get a video of something moving yet, but may have found something.

The clunk happens when braking just before you come to a full stop, and again when starting up from a stop. But it also can happen with no brakes involved like when going thru some switchback curves quickly. Could be wrong but my conclusion from this is that the clunk is due to something fairly massive shifting against metal, like a bad engine mount or suspension bushing. Could also be in the driveshaft, but a quick check did not find any looseness there, and the clunking in turns when speed is constant might eliminate this one.

I was looking at the rear upper control arm (the boomerang) again, and noticed with the jeep on the ground the center "bushing" is tight but I could get some vertical play at the ends, more so on the pass side. Did not know if this was normal or not for those bushings, or if I need to check with the rear wheels off the ground. Can anyone chime in on how much play these end bushings are supposed to have or not.

Anyway I figured I have a go at this this weekend and if I can't locate the source, take it into a shop next week.

WWDiesel · **Posted:** Sat Aug 05, 2017 10:38 am

Those rubber bushings allow for quite a bit of movement especially if they are worn out or the rubber is busted loose from metal mounting parts. :roll:

Keep in mind, the two rubber bushings on the ends of the boomerang are bolted to the body right under the back seat, so any movement of the boomerang that is not absorbed by the rubber bushings in the boomerang and allows for excess movement will make a clunking sound that is transmitted into the body where you can hear it. :shock:

On mine, sometimes if I take off from a dead stop and let of the go pedal just enough to take most of the load off the rear axle, sort of like freewheeling, and the transmission changes up to a next higher gear while it is in this condition, I will get (hear) a loud CLUNK from under rear end. My boomerang has been replaced with a Mopar unit and is fairly new, so I just ignore the sound and mark it up to design of the vehicle. :roll:

And I have checked the lower control arms and bushings and they are all in good shape!

Before I replaced the boomerang right after I purchased the Jeep, there was lots of noise coming from under the rear seat area anytime I rode over a bump in the road. I live on a dirt road with lots of bumps, so I get to test it every time I drive it!!! The rubber bushings on the OEM boomerang were worn slap out, busted, and allowing the metal boomerang to contact the flanges of the body where it mounts. I could see the shiny metal where the two had been making contact....

:SOMBRERO:

Steve777 · **Joined:** Fri Oct 16, 2015 11:31 pm **Posts:** 279

Thanks WW, that does sound like mine pretty much. A big clunk at slow speed starting or stopping or when pulling a tight curve/corner.

Mostly what I was able to check on the outside boomerang was up down motion with a load on them. Think I will try again with the axle off the ground and see if I can get some leverage to check the forward back play.

I feel like I may be getting close on this.

WWDiesel · **Posted:** Sat Aug 05, 2017 4:27 pm

Tip

On level ground, Chock front tires fore & aft, Jack rear end of vehicle up until tires are slightly off ground and not touching, place vehicle body on a set of good safe jack stands, then with transmission in neutral and emergency brake on good and tight. Take a large screwdriver with a long handle and wedge it into rear driveshaft U-joint, then twist driveshaft in a slight forward and reverse motion and observe movement of all rear suspension parts. This will stress all the moving suspension parts bushings including especially the boomerang where you can observe them in motion. Watch carefully the two ends of the boomerang where it is bolted to the body....

good hunting,
:SOMBRERO:

Steve777 · **Joined:** Fri Oct 16, 2015 11:31 pm **Posts:** 279

Well, I have some news to update on this. I finally gave up and took it into the local Jeep dealer who did a good job on programming my extra keys. They found 3 problems: bad front sway bar end links, pass side engine mount and Pass wheel bearing. They told me that they can't get the engine mount from Chrysler any longer as they were obsoleted. [NOTE to those who might be thinking of replacing engine mounts, you may want to pick some up soon]

I guess my hearing was leading me in the wrong direction, I could have sworn the clunk was coming from the rear, but it seems it was all in the front.

Anyway I ordered parts online, and figured I'd have a go at replacing things myself. Sway bar end links were no problem. Wasn't hard to get the nuts off the engine mount. But I sort of got stuck when it came to jacking the engine up to free the old mount. I measured enough clearance at the fan to shroud (1+") so just started jacking up the engine. Well it moved about 1/2" up and from then on the jack was pushing both the engine and body up. When I looked around to see what was hanging it up, it turned out the top of the tranny dip stick tube was starting to contact the tunnel, there are a bunch of wire harnesses there too.

Anyway, I gave up on replacing the mounts for now and just put everything back together. Interestingly though the top nut on the pass engine mount was loose when I took it off, and with just tightening it up again (and the sway bar ends) the clunk is gone (a small victory, for now). Odd that the dealer did not check to see if it could be just the top nut on the mount!

So a few questions:

1. How do folks jack the engine up far enough to remove the mount? Is my lib special with the tranny dip tube hanging things up 1/2 way up? Looks like I could unbolt the top bracket on the engine, but that looks like a bunch of work. Did I miss something? Is there some way to reconfigure things over the tranny so that it can move up all the way?

2. I am puzzled on the dealer's claim that the front wheel bearing is noisy. I had checked that wheel twice (before and after they diagnosed it). There is no side to side or up/down play. When you spin the wheel by hand you cannot feel a rumbling bearing. No difference in noise when you shift the vehicle's weight from right to left, in fact no bad noise at all. Those are the usual tests I have used to find a bad bearing and it passes all of them. Is there something special about these front wheel bearings that I don't know (my hearing is obviously suspect), or is the dealer just trying to pad the repair bill?

Anyway, slow progress being made. Welcome thoughts/ideas on the remaining issues.

GordnadoCRD · **Posted:** Thu Aug 17, 2017 1:12 am

I had no problem lifting mine, but then I did it when everything was stripped down to the block, and the EGR was removed, including the exhaust crossover pipe (behind the block) that could hangup on the transmission tunnel. I also did both sides at the same time, but the RH side one wouldn't give much resistance anyway. It was torn nearly in half.

WWDiesel · **Posted:** Thu Aug 17, 2017 11:29 am

When I replaced my motor mounts, I simply took the top bolts out of the radiator fan shroud. It is two piece shroud now after mod.
Other than that did nothing else; jacked up engine one side at a time and replaced motor mounts. Drivers side was hardest one to do.

As to motor mounts, they are still available through many on-line retailers....

http://www.factorychryslerparts.com/pro ... 011AD.html
http://www.factorychryslerparts.com/pro ... 374AC.html

Driver side motor mount - 52129011AD
Passenger side motor mount - 52129374AC

Google OEM part numbers... :google:

mrhemi · **Joined:** Tue Dec 08, 2015 10:46 am **Posts:** 180

On the motor mounts being obsolete, the dealer probably looked up what are actually the motor mount brackets that bolt to the engine. Those have been obsolete for quite some time.

Steve777 · **Joined:** Fri Oct 16, 2015 11:31 pm **Posts:** 279

Yeah WW, I found parts online for me. No problem for now, but if Chrysler is no longer making them then perhaps we are draining a fixed supply. Of course could be that the dealer just looked up the wrong part number too.

I will check and see if it might be something else binding as I lift the engine. Another thought is I wonder if the amount of lift people have added makes a diff here. My lib is stock suspension at this point, so that may give me less room to play with. If so, then jacking the body up a bit and putting it on stands might get me more room.

Any comments on the wheel bearing?

Slow speed klunk starting and stopping

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