comanche09 Posted January 30, 2010 Share Posted January 30, 2010 Does anyone else have this happen? Bed empty. It happens when going over railroad tracks or when there is an abrupt dip or hump in the road at speeds of like 25-35 mph. Moderately loud "thunk" noise from the rear. What is it? Link to comment Share on other sites More sharing options...
ComancheKid45 Posted January 30, 2010 Share Posted January 30, 2010 Loose Spare tire in stock carrier? Exhaust hitting something? it could be a number of things, likely fairly noticable Link to comment Share on other sites More sharing options...
Wildman Posted January 30, 2010 Share Posted January 30, 2010 Loose / bad shock, broken leaf spring, best to craw under the back end, and if you can, get a helper in the box jumping up and down and look around. Link to comment Share on other sites More sharing options...
comanche09 Posted January 30, 2010 Author Share Posted January 30, 2010 Hmm, doesn't sound like its normal. Spare is tight, shocks are new, springs look ok and all exhaust hangars intact. The leafs are original but look fine, no missing clamps or obviously broken leafs. There is one intersection that I can re-create the noise everytime if I cross it going over 30 mph, there is an abrupt dip in the road. Tailgate has some play at the catches, but thats and entirely different noise (more like a rattle). This is a dull "thunk" Link to comment Share on other sites More sharing options...
Geonovast Posted January 30, 2010 Share Posted January 30, 2010 How good are your bumpstops? Link to comment Share on other sites More sharing options...
sinkrun Posted January 30, 2010 Share Posted January 30, 2010 Mine did this for a long time ended up being those crappy overload or spring helpers coming loose and walking up the spring set thus making them closer to the body at hitting on certain bumps. Also check the exhaust at the crossmeber known to break the round rod that goes into the bracket and cuase a clunk. Link to comment Share on other sites More sharing options...
Geonovast Posted January 30, 2010 Share Posted January 30, 2010 Mine did this for a long time ended up being those crappy overload or spring helpers coming loose and walking up the spring set thus making them closer to the body at hitting on certain bumps. Also check the exhaust at the crossmeber known to break the round rod that goes into the bracket and cuase a clunk. The overload springs are on the bottom of the springpack. There's no way for the to move unless the centering pin broke, and even if they did walk, they'd fall out of the springpack, and make the axle, well, probably slide back on the spring. Link to comment Share on other sites More sharing options...
sinkrun Posted January 30, 2010 Share Posted January 30, 2010 This is a helper spring on top two pieces one in front and one behind the axle tube and they most certainly have came loose several times. If it wasnt 5 degress out I would go get a picture. Link to comment Share on other sites More sharing options...
42mattd Posted January 30, 2010 Share Posted January 30, 2010 Mine does the same thing and I also have no idea why. I've checked all those same points and found nothing. However, I don't recall hearing it when driving without my tailgate. Link to comment Share on other sites More sharing options...
Geonovast Posted January 30, 2010 Share Posted January 30, 2010 Certainly could be the tailgate. See how much play is in it, and adjust the latch catches if need be. Link to comment Share on other sites More sharing options...
ratrapp Posted January 30, 2010 Share Posted January 30, 2010 i've got the same thunk as well.i don't even have a spare tire reciever on mine and have new shocks as well. Link to comment Share on other sites More sharing options...
Dave Stark Posted January 31, 2010 Share Posted January 31, 2010 What about the rubber bushings that go in the eyes of the springs, those things tend to wear in one direction & could be hidden by the frame mount. When i did urethane bushings on mine i wasn't quite able to complete the job before i had to move the truck out of my shop & needless to say it made a very pronounced dull thump just driving it around the parking lot. Link to comment Share on other sites More sharing options...
jeepcoma Posted January 31, 2010 Share Posted January 31, 2010 What kind of shocks are you running? Mine made similar noises when my shocks were maxing out, they'd clunk when they reached the end of travel just like you're describing. You wouldn't be able to tell if they are reaching the end of travel just pushing up and down on the bumper to test if they are still damping. Link to comment Share on other sites More sharing options...
akamcbird Posted January 31, 2010 Share Posted January 31, 2010 i found my thump coming from the leaf spring clamp bolt contacting my gas tank skid... Link to comment Share on other sites More sharing options...
comanche09 Posted February 1, 2010 Author Share Posted February 1, 2010 What kind of shocks are you running? Mine made similar noises when my shocks were maxing out, they'd clunk when they reached the end of travel just like you're describing. You wouldn't be able to tell if they are reaching the end of travel just pushing up and down on the bumper to test if they are still damping. I think this could be it. Would better shocks help with it? I have the cheapo Monroe base shocks. Glad to hear I'm not the only one. Link to comment Share on other sites More sharing options...
possum Posted February 2, 2010 Share Posted February 2, 2010 Both of mine do the same thing. One is a LWB and the other a SWB. Both have new shocks and everything is tight underneath. The couple other trucks I have had have don the same thing I chalk it up as a "truck noise". Link to comment Share on other sites More sharing options...
freakjeep93 Posted February 2, 2010 Share Posted February 2, 2010 ive got a question. does it make this noise with wieght in the bed?if it doesnt it may mean that your bed mount bolts may be loose or that you shocks may be too short and are over extending. just an idea.... Link to comment Share on other sites More sharing options...
jeepcoma Posted February 9, 2010 Share Posted February 9, 2010 What kind of shocks are you running? Mine made similar noises when my shocks were maxing out, they'd clunk when they reached the end of travel just like you're describing. You wouldn't be able to tell if they are reaching the end of travel just pushing up and down on the bumper to test if they are still damping. I think this could be it. Would better shocks help with it? I have the cheapo Monroe base shocks. Glad to hear I'm not the only one. "Quality" of shocks isn't what's important here, it's more question of "travel specifications" and "application". The best shocks in the world won't work if they are put in an application where they only have 1" of upwards travel before full extension, and the cheapest shocks you can find will outperform them if their specifications meet the usage demands. I found the stock XJ specs to work quite well with a regular MJ setup, but as soon as I got about 1-2" inches of lift in the rear from MT springs they completely sucked, because I was operating outside of their intended application range. Post up a part number of the shocks that you're running and any lift in order to help pick out something applicable. Link to comment Share on other sites More sharing options...
comanche09 Posted February 9, 2010 Author Share Posted February 9, 2010 What kind of shocks are you running? Mine made similar noises when my shocks were maxing out, they'd clunk when they reached the end of travel just like you're describing. You wouldn't be able to tell if they are reaching the end of travel just pushing up and down on the bumper to test if they are still damping. I think this could be it. Would better shocks help with it? I have the cheapo Monroe base shocks. Glad to hear I'm not the only one. "Quality" of shocks isn't what's important here, it's more question of "travel specifications" and "application". The best shocks in the world won't work if they are put in an application where they only have 1" of upwards travel before full extension, and the cheapest shocks you can find will outperform them if their specifications meet the usage demands. I found the stock XJ specs to work quite well with a regular MJ setup, but as soon as I got about 1-2" inches of lift in the rear from MT springs they completely sucked, because I was operating outside of their intended application range. Post up a part number of the shocks that you're running and any lift in order to help pick out something applicable. The shocks I got are from O'reillys Auto Parts, they are the ones spec'd for the Comanche and are the cheapest Monroe available (all white in color). The counter guy said they are for 4x2 or 4x4. I will dig up the part numbers. Currently no lift on the rear, 2wd sagging springs (7-1/4" from top of axle tube to base of bump stop at the frame, 1" below spec). I've got some 4wd (probably sagging too) spring I am going to install tonight that should net about an inch of sagging lift. :rotfl2: Link to comment Share on other sites More sharing options...
comanche09 Posted February 10, 2010 Author Share Posted February 10, 2010 Well, I got one of the 4x4 leafs in (need new u-bolts, they don't seem to want to go back through the perch). In the process, I noticed that the limiting factor in downward suspension travel IS the SHOCKS then the BRAKE HOSE :fool: . Link to comment Share on other sites More sharing options...
maddzz1 Posted February 10, 2010 Share Posted February 10, 2010 I would say to check the shackles and see if there are any marks where they may be hitting something. The rear springs may be flexing alot from 20 years of use causing the shackles to hit Link to comment Share on other sites More sharing options...
CWLONGSHOT Posted February 11, 2010 Share Posted February 11, 2010 What kind of shocks are you running? Mine made similar noises when my shocks were maxing out, they'd clunk when they reached the end of travel just like you're describing. You wouldn't be able to tell if they are reaching the end of travel just pushing up and down on the bumper to test if they are still damping. I think this could be it. Would better shocks help with it? I have the cheapo Monroe base shocks. Glad to hear I'm not the only one. Take them off and go for a ride!! NOT fast mind you, but if the noise is gone... you will know for sure. Handling will be touchy, so don't go far or leave them off long. CW Link to comment Share on other sites More sharing options...
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