My truck has recently developed a distinct growl/roar at 65MPH. At first I thought it was simply tire noise as I had just rotated the tires. However, when putting the coals to it heading up a decent incline at speed the noise gets much more noticeable. I have pulled a couple of vehicles out of the snow over the past 2 weeks, one requiring the winch which did drag my truck a bit. What should I be looking for in the drive train? Rear diff fluid is fairly fresh (synthetic - 25K miles), trans fluid is very fresh, (5k miles) Transfer case? Thanking you all in advance for your thoughts/opinions.

 

Check for a rusty dust around your u-joints.