can someone help me with driveline thud

[superdutyscaler]

ill start by saying i dont have a 6.0, but i do own a 2004 f-350 but it has a 5.4 but im in desperate need of some help. for the past 7-8 months when i first take off from a stop i get this thud slip feeling like there is a huge amount of play in my driveline and it thuds and then grabs as if everthing is catching up to itself if that makes sense to everone? I did searches on here and i installed NEW u-joints, greased slip joint, transmission mount, had the gears checked by a axle builder, changed axle oil, tcase oil, tranny oil twice. all with no improvement, also if i put the tcase in 4x4 it gets worse?? Im completely lost now and i have no idea what to do next to try and fix this. im done spending money on things that are suppose to help but do nothing but make me broke. So can anyone give me advice or point me in a direction to try and solve this problem PLEASE? I know this isnt suppose to happen because my dads 2000 4x4 diesel doesnt do it and my buddies 2003 5.4 which is identical to my 2004 except its a F250 and my truck isa F350 doesnt thud or clunk on take off either

[dxusmc]

had something similar to this happen with an old dodge of mine, turned out to be yoke on the tcase was actually cracked and would separate only when torque was applied. Hope that's not your problem but here's a bump in hopes of getting ya some help.

[superdutyscaler]

thanks but i got it fixed, the Mobil1 grease i was using wasnt able to cushion the slip joint in the driveshaft. So i went to the dealer and got the proper ford slip joint grease they sell and its all good now! its crazy how a teflon injected grease can make your truck shift like its floating on clouds

[layson]

glad you got it figured out.