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Unread 12-20-2012, 07:53 PM   #1
justin13703
Registered User
1997  
 
Join Date: Feb 2012
Location: Hagerstown, MD
Posts: 9
Loud Clunk from rear when first applying brakes

I posted this over on cherokeeforum also, but Im hoping to get as many expert's opinions on this as I can get it sorted out. Heres my problem:

1997 Cherokee Sport, 5 speed transmission, 217,000 miles.

When I am driving and apply moderate brake pressure, I get a very loud "bang" from the rear of the jeep. This is usually accompanied by a surge of sudden braking power from the rear, and I can feel it in the brake pedal. This doesnt happen when applying very light brake pressure, but moderate. Also, it usually will only do it one time per each driving cycle. Once it does it, it tends to not do it again until after Ive come to a stop and started moving again. It is not a continuous "bang bang bang..." until the jeep stops, but one single "bang". It WILL NOT do this if the jeep is stationary. It ONLY does it when moving. Also, if I am moving and slowly start pulling up on the e-brake, it seems to have no effect until I get to a certain point, then the "bang" happens and the brakes grab. But the e-brake works normally when the jeep is parked.

Also, I dont know how this could be related, but the other night I was troubleshooting this and took off from a stop relatively quickly, heard the "bang" noise again, and for some reason my back brakes grabbed pretty hard. Like the e-brake was pulled, but it wasnt. I drove it for a few seconds like that and the brakes released somehow. The e-brake handle and cable are new by the way.

The brake fluid reservoir is full and it is definitely not air in the lines. It is a very definite sound, like someone is hitting the underside of the jeep with a sledge hammer when it happens. Hopefully you guys can give me some help figuring this out. I would be glad to upload a video showing what it is doing if there isnt a minimum post count needed to upload vids. Sorry about all the "Bang"s lol.

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Unread 12-21-2012, 02:27 PM   #2
buildin1XJ
Web Wheeler
1999 XJ Cherokee 
 
Join Date: Oct 2011
Location: Knoxville, Tn.
Posts: 1,568
Need to pull the drums off,sounds like something has come apart.Brake springs etc.
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Unread 12-22-2012, 12:16 AM   #3
justin13703
Registered User
1997  
 
Join Date: Feb 2012
Location: Hagerstown, MD
Posts: 9
Ok, I've been hearing it could be the cylinders in there hanging up too. Hopefully it's a cheap simple fix, I'm sure it won't be though lol.
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Unread 12-22-2012, 09:39 AM   #4
tsc
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2006 LJ Wrangler 
 
Join Date: Mar 2007
Location: Pacific Northwest
Posts: 514
could be the rear driving shaft binding on the transfer case tail shaft as the axle wraps.

Solution- drop the rear drive line and grease the tail shaft.
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Unread 12-23-2012, 04:32 AM   #5
wgirvine
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1992 XJ Cherokee 
 
Join Date: Oct 2007
Location: Rosamond, CA
Posts: 603
The rear axle is falling off....

Ok, lots of things to check: driveshafts, axle U-bolts, leaf springs for cracks/bushings, body cracks... but one thing that most people overlook is the condition of the brake backing plates. Take the drums off, clean everything (with brake cleaner, not an airhose) then look at the very small pads stamped into the backing plates where the edges of the brake shoes ride. They should be smooth and flat with no ridges or grooves.

I've seen backing plates that were so worn, the shoes wouldn't expand; they were caught in a groove. After enough pressure was applied, the shoes pop out and the brakes work. It's really important that these little pads be smooth for proper operation of the brakes. If they are worn, the only fix is to (a) replace the backing plate or (b) weld up the worn pad, then have a machine shop mill them back flat again.
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Unread 12-23-2012, 03:56 PM   #6
justin13703
Registered User
1997  
 
Join Date: Feb 2012
Location: Hagerstown, MD
Posts: 9
Awesome guys good info. I'm pretty much narrowing it down to the tail shaft, cylinders, or the shoes/backing plates. This is gomna be the first thing I tackle after I get moved into my house here in a week or two.
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