i've noticed this now 3 times......

the first couple times i thought i was just hitting a bump in the road...

the 3rd time my girlfriend was in the truck and she felt it too....

all 3 times i have been coming out of a turn from a stop and accelerating slowing...... then the CLUNK happens... feels just like hitting a pot-hole.... but he road is smooth..........

again, it's only happened 3 times on me so far so it's it's not consistent...

ugh...... luckily I will be buying an extended warranty soon... even though the truck only has 2,500 miles on it.....

man i figured my truck would be ok as it was built only 2 months ago......

 

I'm hearing the same thing from my F-150, hear/feel it on light 2-3 upshifts. Feels like too much slop in u-joints. Does not occur under loaded shifts only light up and down shift. I'm looking up T.S.B's for same issue. Knowledge is very powerful when trying to describe to service writer at dealership. My experience has been that they just stare at you like a deer in the middle of the road! I feel for the tech's as they have to try to fix something based on some cryptic note from the service writer.

 

Mine occurs very rarely in normal driving, but I can recreate it pulling away from a stop when I let off the brakes, allow the car to idle forward a few inches, then kind of goose the gas. I hear and feel a very faint clunk. This happens whether or not I am turning. Is this a problem with the torque converter? Or is this just normal?

 

I get it every so often on turns, its the limited slip unit.

 

I've been on a few other Ford truck forums and from what I have seen this is the biggest problem with the 04's and sound like no change in the 05's.

I've had mine at the shop. There are two TSB for this. The first one is TSB 04-26-6 .They remove the driveshaft and lubricate the slip yoke with teflon grease. They also add a friction modifier to the rear diff but this is not listed on the TSB but was on the work order.
The other TSB is 04-17-5 and is the replacement of the limited slip clutch pack.

The first seems to have made a small difference but there is still a problem. The rear end now seems to have develped a whine which is also a common issue.

Making an appointment to get these issues addressed..

ps The vibration is only from a start when the rear end is cold.. The whine is at highway speed.