I have a ford f150 crewcab 4x4 2001, I too have a popping noise from what seems to be the rear end of the truck, but I also have noticed that the truck pulls to the right, the right tire is worn on the outside edges, and yesterday I noticed that right behind the front tire is a arm that attaches to something below it (I am not a part kinda person ) and the bolt is broken. I am afraid to drive it and do not know how long that bolt has been broken, it is completely unattached.

 

I had a 98 F250LD that had that problem every time I made a right 180 into the approach at Burger King which also had a 30 degree or better incline and placed my frame and suspension in the extremes of its normal range of travel. After some extensive investigation I finally found that the duals that the previous owner had installed were being clipped by the rear of the lower short spring and once it even got hung up on there. Well, the chrome tips were rusting through anyway and I hated the sound of the single 1 7/8 id glasspack with two tailpipes jerry rigged to the outlet so I had the y pipe cut and installed a lightning muffler and tailpipe assembly. All of the factory hangers were placed on my truck and it looked like it came that way. It made good sound, not so loud it woke the cops from their naps and gave excellent performance improvement. Never heard the clunk noise again.

 

Some of you with this particular problem may be experiencing torque wrap-up at the slip yoke. The change of geometry for the suspension and drivetrain during initial takeoff may be causing the slip yoke to bind on the output shaft and when it finally breaks free, it causes a loud clunk. You may notice that there is a slight snap just before the loud clunk. Ford has a temporary fix for this on the new trucks by putting grease in the slip yoke. If they don't get it fixed before my truck goes out of warranty, I'll have to ask for a new replacement truck or to buy mine back. This issue can be found in the service manuals of the '98 F150-F250. I'm sure it's probably found in those of other years as well.

 

If I had to guess I would say the Sway bar link bolt snapped. Is it number 10 in the picture below?

JMC

 

Well, I live in Wisconsin/Minnesota and have a 1999 4x4 Scab and have the same sound. Once again, gas tank near empty, wet conditions, turning into parking lots or driveways. Has anyone else found anything? Only started doing this when cold and wet outside. I was thinking that it could be the gas tank moving around. Someone else said to check the leaf springs to make sure they arent hitting the exhaust or the gas tank itself. I'll report when I find more.

 

It's been around a year ya? for this thread? I have found nothing, no real pattern or anything outside of the damp and cool temps theory. Even my buddy's Sport trac has it and I say ya just gotta live with it. I really think it's just expansion or contraction of rubbers and stuff and really nothing to worry about. I have a strange whistle too and cannot locate it. I'll bet it's a pulley but we'll find out one day. Right now it's pretty quiet almost non existant.

 

I just fixed the pop or clunk in the rear of my truck. Like mentioned in this thread mine got worse in wet weather. In the 2004 & up sectioned someone suggested lubing between the leaves of the rear springs with a spray like WD-40. I tried that and it didn't work. Next I tried spraying the shackles and the problem got worse, just like when it gets wet. I checked the shackle bolts and found the lower rear shackle bolts had loosened. I tightened them about 2 turns each and no more pop.