thump when accelerating
 

when i accelerate from a dead stopthere is a thump or some kind of a slip in the drivetrain. im pretty sure its not my tranny tho. i dunno if my leaf springs r loose or if its my driveshaft. needs sum feedback. thanx:beers:

Maybe a motor or tranny mount?

I get the same thing with my 1997 F150 4x4. I think what you are hearing is the driveshaft slip joint (spline to trans) hanging up upon acceleration. This is a fairly common condition on some of these trucks. I have removed the drive shaft twice and applied grease to the inside driveshaft spline, reinstalled and the noise goes away for a while only too return again. They suggest Teflon grease for this as it is suppose to last longer. There are some guys on this site with some good information regarding this problem and a Ford TSB out also. I will try and find the TSB number and post it here for you. I am only guessing this is the same problem you are experiencing. Good luck.

dynotech:
thanks for the reply. i was thinking something along those lines. i will try and find some teflon grease and see if it works for me. once again thank you it has been annoying me for some time now

I'm having the same prob, took it in and yes they said it was the spline thing. They are going to grease it up when I bring it back in.

Id take a look and see if your rear driveshaft u-joints are bad. My truck used to do the same and when I pulled the driveshaft I found that the rear joint was bad. Pretty much most of the needles fell out and it wasnt moving smoothly. I put on a new set of u-joints and now its silky smooth.

yea make sure ur u joints are good...i thought my tranny was goin out so i had a mechanic drive it around and he thougt the same thing i did that it was the tranny...but i changed out the rear u joint and it was 100% smooth again like new...if its auto. check and see if it clunks when u take it in and out of reverse...

years ago i had a thump in my driveline. new truck with 50,000 miles on it, dealers couldnt figure it out but i did.
i got up under the truck, grabbed and shook everything as if it were being used ( twisting drive shaft, moving rear end up and down, etc......)
it ended up being a bunch of sand and dirt worked its way under the tranny mount, and was causing the slight thump.
unbolted the tranny mount, cleaned it up and put a layer of chassis grease between the crossmember and the bottom of the mount.
fixed that annoying Ka-Thump when you took off!!!!

I have the same thump on my '99. It started out at one thump now it does it 3-4 times when accelerating. I didn't feel any slack in the drive-shaft and whatnot...Guess Ill have to take a closer look.

I had the same thing a while back, I swore up and down it was in the tranny or axle, then one day I looked at my battery and notice it had been sliding back and forth! tightened the clamp and no more thump! It sounded 100% like it was coming from the back, and it even felt like it... just a thought

I know for a fact mine is coming from under the truck. I can hear it echoing if I'm at a drive thru close to the wall. It only happens when I accelerate from a stop but....It does it a few times when the truck is off and I step on the running board(no its not the running board), which leads me to believe its in the suspension somewhere?

I had a thump too. You can see where there was a plate, kinda dumb set up. But I took it where we take the 18 wheeler and put a bottle jack under with the plate in place and welded her up. I had to put a new trans mount after cuz of the heat, what a SOB that was.
https://www.f150online.com/galleries...073-183972.jpg
https://www.f150online.com/galleries...073-183973.jpg

Thump also in 2007 Scew
 

I was looking through the forums for the exact same problem. I have a 2007 scew with only 5000 km and my truck start to develop the same thump at accelerating. Mine also happens only at a dead stop, and usually doesn't happen if I accelerate very slowly (or idle away from the stop). I find it very annoying that my new truck does this. I haven’t towed anything yet or overloaded the bed. It's only 4 months old; it shouldn't be making noise already?

Anyhow, I'm getting concerned and thinking about booking it in at the dealership to let them fix it. Does anyone else with a new vehicle have the same issues?

you should be under warranty. take it in and have them look at it.