My life experience is that whatever is wrong will resolve when I get to the shop or Dr.s office. I let everything go for two weeks to make sure I have a problem. Doing that with the chest pains was almost the end of me....to soon old. This pertains to that mysterious "CLUNK" coming from under the rear of the truck as heard from the cabin. The day before my mech appointment I began to notice that the clunk had expanded from when I start the vehicle to whether I was in gear or not and didn't change if I left the trans in neutral or 1st. Then I noted that it clunked when it was sitting there running at idle and sometimes if I sped up the rpm to 1500. Sitting there pondering this with the engine running i happened to spot the tach b a r e l y dip when I heard the CLUNK. Just a tiny dip of the needle, mind you. That CLUNK is what I hear from a misfire that is muffled and then further attenuated by the cab. Sure sounds like a diff clunk and I have heard many. Darn Ford!

Were I to go out behind the vehicle I am sure I would hear that deep "PUT-POOF" at the tail pipe. I have no error codes. Seems to run OK but I think that noise is becoming more regular. I can wait till somthing catches fire or the engine quits but does anyone have an idea what this might be?

thanks

 

There is a slip joint in the driveshaft near the transmission that clunks on take off most notably. It needs grease. My old black ranger would clunk in 4wd when taking off. Check that slip joint where there is a boot on the driveshaft and check your u-joints to start off with. Check the diff and t-case fluids if you haven't.

 

Thank you Alex. I have the drive shaft sched for a complete work thru and I know that a u-joint has end play as when I start the drive shaft goes PIN BG and rings for a while. That is the ujoint sliding from side to side as it must do to find center and noit vibrate but mine has way to much play and initially in the turning slaps into the other end like a hammer. It has done this for a long while so I know it isn't the CLUNK.

My CLUNK can be heard sitting there with the engine running. Every once in a while CLUNK. The noise is coming from the muffler and must be a subtle back fire. More like a miss. Outside it sounds like a PIFFFUT than mechanical but inside the cab it sounds differential....

 

Ah then check your plugs, wires, put dielectric grease on them. Might be worth doing a seafoam treatment through the gas tank, then through the intake, and finally right before you change the oil put it in the crank case and drive it for a week. Will help to clean out the engine and the valves, seals etc. If what you're telling me sounds kinda like a random misfire. I may be wrong though.