Need help identifying a drive train noise in my "new to me" 85 FJ 60 with 190k on it. the noise is a low groan or howl with a very slight metalic or gear whine and is quite loud. It occures only when the vehicle is moveing and changes pitch with vehicle speed. It seems to lesson above about 40 mph.The niose occures in all gears and in neutral clutch in or out.all drive train fluids have been changed with new 80w90 gear lube and lucas oil additive. clutch feels good, u joints are tight and have been lubed, no slop in slip yoke eather. Rear wheel bearing area is dry so i dont think the bearings are bad. I jacked up the rear and ran the truck in gear to listen for the noise but was unable to pin point it but I know it isnt in the front axel. any ideas?