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Unread 04-01-2013, 02:05 PM   #1
zjosh93
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1993 ZJ 
 
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Front end clunk on railroad tracks

On the road from my parents house to my house there is a set of railroad tracks and while they are no problem for my mom's Focus or my girlfriend's Lancer when I hit them in my ZJ it sounds like I'm running over a full curb. They are pretty smooth tracks too. It started doing this about two years ago, before that all was well.

I've swapped out all the control arm bushings in the front and the front shocks. Before that I could see where the driver's side axle bracket for the upper control arm was hitting the motor mount. The sway bar bushing are newish polyurethane. I've checked the ball joints and the rest of the steering linkage. In fact I got it alinged about a year ago and the guy complimented my Jeep on it's well maintained front end.

The only thing I can see is that the bump stops are in pretty bad shape. I'm not sure that enough is left of the driver's side to do much of anything. I don't think the railroad tracks are enough to get the axle into the bump stops though and I think that hitting the bump stop would be jarring no matter what.

Any ideas?

Any good places to get a set of stock front bump stops?

Thanks

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Unread 04-01-2013, 02:25 PM   #2
mig1289
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Did you get new sway bar end links when you did bushings?
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Unread 04-01-2013, 02:28 PM   #3
zjosh93
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Put in new polyurethane bushings in the sway bar links and new poly frame bushings as well when I bought it about five years ago. They still look perfect.
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Unread 04-01-2013, 05:35 PM   #4
zjosh93
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Forgot to mention that I can run over speed bumps and speed humps as fast as I want and no clunk.
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Unread 04-02-2013, 04:57 PM   #5
Foundrydude
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Change the bump stops. If it still does it change your motor mounts. Or slow down over railroad tracks.

If you're driving aggressive at all, it's gonna be on those bump stops frequently. How do you think they got so tore up!

What most drivers perceive as the last inch of suspension travel, is actually the bump stop

good luck!
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Unread 04-02-2013, 05:05 PM   #6
zjosh93
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I also forgot to mention that I replaced the driver's side motor mount (and filled the voids with polyurethane). The passenger side looked fine. The bump stops are really dry rotted and have been since I bought the Jeep. I can rub bits of rubber off with my fingers.

I guess I should replace the bump stops but I'm kinda at a loss as to where to buy some. All I see are universal pieces but mine are in bad shape so I don't know what length etc. to get.

Ha! Yeah, not planning on driving less aggressively.
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Unread 04-02-2013, 05:54 PM   #7
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How about your trackbar bushing(s)?

Stock trackbars really only have the bushing at the axle end, but it can get noisy if it's broken down - noise travels up the TB and resonates through the frame side mount.
Agreed on the bumpstops, but not overly likely in my opinion.
Are the control arm bushings fully seated in the CAs? If you're running stock CAs, it's very difficult, if not impossible to get the bushings seated perfectly.
Have you ruled out bushing issues in the rear?
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Unread 04-03-2013, 08:54 AM   #8
zjosh93
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Hmm... I don't specifically recal checking the track bar bushing. I think I just looked it over but I didn't pry at it. I'll check it out Saturday.

I bought complete lower control arms and pressed in new bushings on the uppers. I cut little spacers from wood to support the arms as I pressed in the bushings so they were completely flush when I was done.

The rear bushings all look fine and don't have a lot of play when I pry at them.

I'm going to look over all the bushings again on Saturday, maybe take out the front springs and cycle the axle up and down to check for problems. If I can find some new bump stops I'll change those too.
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Unread 04-06-2013, 10:02 PM   #9
zjosh93
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Checked the track bar bushing today and it was fine. The bump stops are trash though, the left side has dry-rotted to the point that only about 25% of the thickness remains. There was also a shiny bit on the lip of the cup so I'm pretty sure the bump stop isn't doing it's job. I'm going to order some Daystar poly stops and throw them in next weekend.

Thanks for the help.
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Unread 04-06-2013, 11:50 PM   #10
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That might help some, but I'm thinking your suspension is bottoming out more than it should.

Tired coils come to mind.
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Unread 04-07-2013, 07:08 AM   #11
96zedjay
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If you suspect a spot may be hitting, stick a wad of chewing gum there. If it is indeed making contact the gum will give you a visual.
My 96 developed a clunk, Immediately suspected sway bar link. Thats what it sounded like. When I looked it wasn't broken. Kept getting louder and louder. (6 MONTHS, 6k miles) Looked and looked at front components and everything was tight. PO at some point had replaced CA's
SB bushings and links, tie rods and draglink and trackbar.... Hmmmm WTF.
Finally, when changing oil and filter I went over everything again and found that when the PO did the SB links he must not have got the driverside throughbolt tight...
Just enough that after time it had wollowed out the hole....The shank of the bolt was worn down to almost 1/4".
Replaced bolt, torqued it properly and shes quiet as a church mouse.
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Unread 04-13-2013, 09:37 PM   #12
zjosh93
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New bump stops fixed it. Hit the same spot and felt the axle hit the stops. It's a set of tracks at the bottom of a little dip in the road so the suspension is loaded when you hit the tracks. I'll keep an eye on things and see if I'm bottoming out a lot. I'll look at new springs if that's the case.
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