Power Problem any Ideas???

[jmalisan]

i have a 1999 F-250 HD that has been a great truck. Recently while pulling a snowmobile trailer with 4 machines on it in the mountians. When i pull the shifter in to four wheel drive i get a loud vibration and there is no power. I am able to get to about 25 mph but no faster with the pedal to the floor.
does anybody have any idea on what could be wrong? I was thinking that my fuel pump may be clogged or maybe my turbo is starting to go. Before i start taking pieces apart was wondering if anybody had any idea where to start?
Any Ideas? or Comments would be greatly appreciated!!!!!!
Thanks Jayson

[HunterJ]

Unless its smoking(Black Smoke) it probably isnt a turbo problem.