[Asked this over in FB Nation and T/A Country as well... suspect I'll receive same responses, but asking anyway due to similar foundation -- not that I want an echo chamber ] Since before rebuilding the suspension front and rear, I've been hearing a mild cyclical howl from the rear of the car while under load. Thought it was from my tailpipes (driver side rubbing on the left rear tire, pass side stuck tight against the shackles). Took to an exhaust shop yesterday and they heated/bent the tailpipes into position so they're not touching anything anymore. On the drive home heard the howl again but louder. Gets more noticeable w/ greater speed, disappears below 20mph or when taking foot off the gas. No vibrations though. Slow going or take foot off the gas above 20mph and it goes away. Checked the rear tires to see if either are rubbing anywhere else -- nothing. I had the rear end apart when I did the suspension to replace bearings and axles (one axle was chewed up). It's a 3.42 posi and everything seemed clean and in good condition when I had the differential open to replace the axles/axle bearings. I'm stumped... Unsure whether this is related... and this is my 1st car w/ a posi. The car shudders when making tight turns into or out of parking spots, just learned this may be because the clutch packs are slipping for the wheels to catch up w/ one another (rears are 275/60/15)? I didn't use posi additive in the rear when I refilled, but used Lucas Oil 75/90 synthetic which Lucas says doesn't need the posi additive. I attributed the shudder to the front tire rubbing at full lock, but now wondering. Research on the world-wide Inter-Lie shows a preference for dead dinosaurs w/ posi additive regardless of whether the lube manufacturer says it's not needed. My course of action right now is 1) add posi additive and drive, see if it changes; 2) dump the synthetic and replace w/ dead dinosaurs and posi sauce; 3) take it in to have the ring/pinion and carrier inspected... All thoughts and insights appreciated. Thx.