I have recently finished a repair on my 1995 Chevrolet Suburban. (4wd 5.7 automatic 4 spd)163k miles. I replaced the rear main oil seal and oil pan gasket(engine in). While undertaking that project I went ahead and replaced the the rear differential (yoke) seal and rear gasket on the differential, both the rear universal joints and front driveline joints, along with both front and rear seals on the transfer case, transmission rear seal, transmission gasket and filter & a O2 sensor. After re-assembly and putting everything back together I have run into one noticable problem. At approximately 55mph a noticable " hummm" comes from the rear end. I put approximately 3 quarts of 80-130 rear end lube in the differential after yoke seal replacement. This noise was not there pre-existent to my repairs. The noise does get louder as you increase in speed. Is it possible that I overtightend the yoke nut for the differential : . Is there a torque specification for this nut. : If this is not the problem is it possible for the driveshaft to be installed 180 degrees out of rotation and would that make the noise that I am hearing. There is only slight vibration that I can feel at approximately 70 mph. I am absolutely positive that the torque converter had been realigned with the original installation holes in the flywheel. Suggestions as to what I need to look at that may be causing this noise. Tires are balanced and rotated.