2001 F350 PSD transfer case

I need to know if anyone has experienced a loud noise coming from the transfer case. When I get in the throttle faily heavy it sounds as though the transmission is coming through the floor board. Every thing else under the truck has been checked and appears to be fine. The only other indication is a slight vibration at around 75-80 MPH. The truck has 90K miles on it and a six inch suspension lift, 35" tires. Aside from the afore mentioned problem the drive and ride are fantastic. Thanks for any help.

I would check the u joints and make sure you have the proper spacer for your driveshaft bearing (if equipped) The u-joint at the transfer case may be going out.