Background 78 K10 no lift running 350/th350/203 10F/12R. I bought the truck a little over a year ago for D/D and plowing. When I first got it, it had a few leaks and vibrations. I changed the yokes on the t-case and rear pinion and put new u-joints in driveshaft (and had a shop balance it). The vibration was gone........ Now... after having the tranny launch on me (rebuilt) and rebuilding the 203 (while it was out), at some point this winter I developed a nasty vibration at about 65MPH. I have tried running the truck in 2nd gear to see if the vibration occurs any differently but it doesn't, which would lead to it being speed related rather than RPM related. At first I thought it was an out of balance wheel/tire (as everything else should be fine), but I just swapped out wheels/tires (I have one set for the summer...Bling/Bling, and one set for plowing in the winter), the ones I had on there were 31 x 10.5 R15 "mud terrains" and the new ones are 31 x 10.5 R15 "all terrains". The vibe is still there (same speed), but it does "seem" to be more noticeable. I am planning: To have the driveshaft checked AGAIN (out of round and/or out of balance) Rebalance the tires (don't think that's it) The question is would something else cause this? Tranny/T-case Drums Could an axle be bent? Any help (or past experiences) is GREATLY appreciated as this is driving me nuts. A heavy vibration at cruising speed on a daily driver, can get old real QUICK!! /forums/images/graemlins/angryfire.gif Thanks in advance.