I took the K5 out for a romp in the mud this past weekend (have lots here in Oklahoma) and started to notice a vibration around 55 mph (under load and coast). Went away at 60 and came back at 70 but disappeared around 75. Had it to 85 indicated and didn't notice it (had sheet metal bucking all over the place and backed down). I have a four inch lift with 33x12.50x15 BFG AT's. I dropped the transfer case cross member and put the 1" spacer between it and the frame tonight. I also re-checked all the u-joints (all new) and checked to see if there was any play in the slip joints, and made sure everything was tight. Nothing. There are several other areas that I'm going to check, tire balance/pressure, front end alignment, etc. There is also one other are that I'm going to adjust and that is the trim piece that bolts to the frame between the rear bumper and the body. It's touching the body and may be causing this (transmiting noise from the frame and amplifying it through the body). It's not noticeable as an out of round vibration but more as a harmonic humm that can be felt in the steering wheel, column, door jam, transfer case shifter, and heard. My question is mainly about the drive shaft orientation. I read another post somewhere that said that the big weight on the drive shaft goes towards the rear axle. Mine is on the slip joint end which mates to the transfer case (reversed). There is a smaller weight that is welded at the other end. Is this the way the driveshaft goes in, or does the slip joint go towards the axle? The drive shaft went back in the same way I took it out but this is not to say someone else put in in backwards. I have the headers disconnected right now to fix an exhaust leak (inspection due next month and that ticking sound was driving me crazy, it's a leak and not a valve). Thanks ahead of time. It's late and I got to get up early in the am.