I own a '99 4X2 Supercab, 4.6, Automatic, with approximately 20,000 miles. Recently I've noticed a very slight thump or bump, when beginning to accelerate from a standstill. It makes no noise and does not happen every time. At times I've thought it might be the rear brakes releasing, but I really can't tell. Also, since these are discs, I don't think they would produce this type of feeling. Has anyone else out there experienced this?

 

I, too, am having a problem similar to you. I've got a 2000 w/ the 5.4 and about 26,000 miles. It doesn't happen everytime, but it sometimes happens just as the truck comes to a stop or as I move my foot off of the brake to the accelerator. It makes no noise and I can't determine what it is. It feels like there is "slop"
with the brakes or tranny. Any ideas? Thanks

 

I've got the same on a 99 Expedition 5.4 4X4. I have positrack front and back, and have been under the impression it has something to do with that. Truck has 17K on it now, has been doing this since about 8K, not getting worse.

 

I have it too. It feels like there is a slight hesitation before I start to move, like play in the universals or something. I only have 2700 miles on my Screw but am just going to wait until it gets worse or breaks. That is what the dealer would want anyway. It is intermittent also.

Would like to know what it is.

Maybe someone can shed some light!!!

 

I had the exact same problem with my 97... try this...

Get about 6 or 8 friends to pile into the bed (I'm not joking). Accelerate the way you do when it makes the noise. If it still makes the noise, I have no clue. If it doesn't make the noise with the weight on it, it's probably something in the rear spring-pack shifting around when the truck is unloaded. I had mine in 4 or 5 times before they even narrowed it down... they replaced the bushings, shackles, lift blocks, etc, until the only thing left was the spring pack... THAT finally fixed it. Put 40k on it after that and it never returned. The way I discovered it was that I hauled a load of lumber for my dad, and it did it on the way to the yard, and after we dropped it off, but not when it was loaded.

-Joe-

 

I had the same problem described above. I can best describe it as a clunk coming from the rear of the truck. It occured either when I came to a stop or when I accelerated from a stop. I had it in the dealer six times. They always said it was a drive shaft clunk. They greased the drive shaft yoke the first three times but this never seemed to correct the problem. The last time the dealer actually replaced the entire driveshaft assembly but this still didn't help. Finally I had a friend suggest adding a leaf to the rear springs. This stiffened up the ride and corrected the problem completely. But after about 2000 miles the clunk has come back. It seems it does have something to do with the rear springs since by addind a leaf temporarily corrected the problem. When you said you replaced the spring pack, was that the entire spring assembly and bushings. I am willing to try anything since I am desperate for a fix. Thanks for any information.

 

I had the same thing last two winters. Goes away in summer. Could be rear springs But I think it's the slip yoke move in and out slightly. I've read it will go away if you lube it. That would sort of explain it going away in summer (any grease on it slips easier).

 

Mine pretty much only does it first thing in the morning, and then only for the first several stops, then quits for the day. I don't so much hear it, as feel it, sort of a thud from the rear, but really muted. The lube sounds reasonable, which would explain it doing it only when cold, not that it gets so cold here, even at this time of the year, but its all relative.

 

I had a 99 4x4 that did the same thing....they greased the yoke twice, but it was a temporary fix...they replaced the entire drive shaft and the problem went away for good.

Now, I have a 2001 Screw 4x4, and I guess thay must have put my old drive shaft in this truck....same damn problem

Back to the dealer again.....

 

Hi everyone, I have an opinion on the drive line thunking when coming to a stop or taking off slowly because I get the same thing on my truck. I come up with my own conclusions because the dealers drive managers or if I get passed them, the mechanics could not figure out. I understand the thunk as a function of transmission relaxation and differential twist/torque and also the brakes holding the differential at a position other then a none running position. When coming to a stop most of the time the RPM's are higher then idle so I beleive the transmission has pressure and when completely stoped, the engine drops to idle RPM's and the transmission lets go and you get thunk or when you release the brakes also and depending on if you got there real fast on a short distance or got there slow you get the thunk or you don't and also depends on weather temp's, that is if your truck is running hot because of summer or if it is winter. Also when taking off from a stop if you give it some gas and then ease off on the gas and then reaply gas you get thunk sometimes. These are my obsevations and I hope they help on understanding this concern because the dealer mechanics either they see it broken or they don't and on the mean time we have questions they can't answer. By the way my truck is a 2001 Supercrew 2WD LSD.

 

Mine does the same thing except it sounds like it's coming from the front left side. Sure every time I take it to the dealer I can't get it to do it again. It sounds like there is slop and then all of a sudden it engages(clunk sound).
Later,
Craig

 

this is likely apples to oranges, but I had a similar problem with my 98 Ranger 4WD before I traded it for a 2002 F150. With the Ranger, the thump was drive shaft-related (a known problem with the early 98 4WD's), and the fix was to replace the drive shaft and yoke. Folks on the Ranger boards mentioned that the yoke needed to be lubricated every so often also. In my case, the problem (i.e., the "thump") was much more noticeable in hot weather, and barely noticeable when it turned cold (OK, cold by TX standards Had the driveshaft/yoke replaced at around 15K, and that seemed to do the trick.

ernie

 

At least he is describing the same situation I had when I discovered the fix for my "clunk".

Mine would do the clunk thing after coming to a stop and then starting again. And empty. Had the bed loaded up with some bricks and no clunk. Empty to go get another load, clunks..... loaded, no clunk.....

I was not happy with the way the truck would sag with only 1000 #'s in it. (almost to the stops!!), so I added some overload springs. The kind that have large U bolts on the ends to 'pull' the overload springs down. It puts an "upward" load on the leaf springs. At any rate, the first thing I noticed on it's test drive was that the clunking stopped. No matter how hard I stopped or started, no clunk! Then, as another added bonus, the road was wet, and on one of my "hard" launches, the rear tires broke loose (3.55LS rear), and NO WHEEL HOP this time!! Man, I was in heaven......... It also solved the sagging problem. I still only put 1000 #'s in and it only drops an inch or so now....