I have an 05 D 4.7 with a thump when ever I hit the gas pedal.
It never happens while in between 0-15 mph. but it happens every other time.
Once the truck slows down then I hit the gas I get the thump.
Dealership keeps telling me it's normal for the 2nd gen D.
i've been fighting with the dealership for two years.

 

Don't forget about a loose pinion yoke or transfer case yoke{also probably covered in Hydra's u-joint answer but I'll ask anyways}check the tranny mount, and does it do it with the vehicle in 4wd on Mark's question and a possible torque converter problem on Rob's=does the truck shift funny? and did you have the fluid changed recently?
and does it do it with the overdrive off?how bout in 4wd?

 

Yes I'm thinking a U-joint.

Take it to a different dealer befor you warranty goes out!

 

my wife had a similiar problem in her 06 durango she took in and had to have the transmission recalibrated and updated. you might wanna try that along wiht the other suggestions.

 

Get under the truck and rotate the driveshaft back and forth (actually wiggle it back and forth, y'know left right left right) and if you can feel is clunkin its a U-joint.

 

Hello everyone;

I will check on all of your suggestions, I will post if I am able to find the problem.