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I have been looking for the source of this clunk for roughly 6 months. It happens when the rear of the truck has body roll, when slowly navigating tight turns and bumps. When it started, I immediately thought it was from the sway-bar links and bushings. I replaced both front and back links and bushings with no change. I removed both rear shocks and inspected the J-clip nuts that secure the top shock mounts. I found that 1-of-4 was cracked through and was causing a noise. I replace all 4 with new bolts and attaching hardware. I removed the front driveshaft, greased the slip yoke, drove w/o front shaft in, no relief. I replaced the rear shocks, to eliminate any issue with internal failure or bushing failure. I reinstalled the front shaft and did the same on the rear shaft, no relief. I did notice the slightest play in the rear shaft U-joints, ordered and waiting parts. Front and rear leaf springs were replaced, from ATS in 2017. I have had 2 mechanics look at my truck recently, took them for rides and they both could clearly hear the "CLUNK." Neither can find anything wrong that would point to the source. They said that everything safety-wise is good, but it will likely get worse before it can be definitively identified.
I have done numerous on-line searches, watched countless videos, and searched through every forum I can find with nothing definitive. I am thinking that it might be body mounts at this point. I even ordered a "Go-pro" style camera to help me identify where this is coming from, arriving this week. I was about to just order a full set of body mounts today, and out of no where the noise stopped!?!? It has made the hair on the back of my neck stand up for 6 months, and suddenly is gone. Does anyone have any additional suggestions? Does the fact that it stopped help point to anything specific? I imagine that it will come back, but I will enjoy driving it in peace while I can. I appreciate any help, thank you in advance!
One thing to consider, though it may be far fetched, is your u-bolts. When I changed my springs, and then drove for around 500 miles, I found mine to be loose. IT caused a clunk sound when hitting bumps, going around corners, and sometimes under load while accelerating. Being that you had hem changed in 17, may not be the issue, but it's something to check (and free).
Did you have something stored in the back? Was it a click or snap type noise or a regular clunk like dropping a log? Maybe something stuck in the bumper or rocker and it finally fell out? Hopefully it doesnt return but if it does, audio/video will help.
Well with all this extra time at home, I went ahead and ordered everything to do the body mounts, clean and coat the under carriage, and several other projects that I have pushed aside. Hopefully I can locate the problem during this evolution. It might take some time, but I'll post the results when I'm done.
Resurrecting this thread with an update.Yesterday I started the rebuild. Pulled off the winch and Ranch Hand bumper. It will be easier to change out the front two mounts. Plus I have to swap out the water pump at some point. Picked up a bulletproof unit to replace when it let go, but I figure now is the time while I am tearing it all apart. Got the tank pulled and started pulling the hitch down. Hopefully I can get started on the body mounts tomorrow. I hope during the tear-down that I find the "smoking clunk" that has been driving me crazy. Since I already had the rockers replaced on both sides, I plan to clean and undercoat the chassis while I am at it. I will post back when I can get back at it, and hopefully identify the culprit.
Thanks to ASFC27FTFBQ and ExxWhy, I am using their threads as reference material to help with my efforts. Below are links to their threads.
After almost 2 weeks I finally got my Excursion put back together. Replaced the fuel sending unit, found that the lower plastic housing was completely broken off. Even had small plastic pieces wedged into the fuel feed line. The rear body mounts were shot. I had read every how-to I could find planning for the worst case scenario's. I sprayed all the mount bolts down with Aero Kroil prior to tear down. I had no problems changing out the rear 10-of-12 mounts. The biggest problem I had was with the front mount on both sides. I had to reuse these 2 bolts only, but the threaded insert refused to completely un-thread. I had to cut off the top with the sawzall and used the angle grinder to cut off the sleeve without damaging the threads.
I cleaned up and coated the chassis and body panels, hopefully keeping it together for many years to come. I used S&B mounts, and couldn't bee happier. This "clunk" was driving me crazy for entirely too long. It was priceless to finally drive the truck again without hearing that annoying clunking from the rear of the truck. If this did not fix my problem, I would felt completely defeated! I used ford mounts for the fronts and noticed almost 3/4 of an inch increase in reveal between the headlights and the top lip of the bumper. After 246k on the factory mounts it was evident that they were severely worn. Replaced both front and rear driveshaft u-joints, both rear emergency brake assemblies, dust shields, wheel bearings and seals. I still have to change out the water pump, but I need some time to recover after this adventure.
I can't keep the same pace I used to, but luckily I have time. I recommend the links I previously included. Those write-ups covered everything perfectly, including some problems that I did not run into. Thanks again to ASFC27FTFBQ and ExxWhy for documenting your efforts.
I had a similar racket and couldn't find anything loose. As I was laying under it looking around I grabbed the shock for the heck of it not expecting anything and it made the same noise I had been hearing. The bushings on the passenger side shock were totally gone top and bottom, the ones on the drivers side showed no wear at all. It still don't make sense to me, and have never had that happen before. Anyway at least there is no more racket.
Phantom rear-end "Clunk"
