i have an 94 f150 2wd with the m5od trans. i have a howling noise like a rear end would make but i changed the fluid on the rear end checking everything inside there and found no problems with the gears meshing, or any metal shavings. also my friend noticed it doesn't howl when i accelerate only when im cruising or decelerating with the engine. could this be the output shaft bushing or bearing. the drive shaft does move a little when i checked it out. i just want to know if the output bearing would make the same noise as what i described.

 

Make sure your pinion nut (at front of pinion shaft by universal joint) is tight. If not search on (pinion nut) or post back.

 

checked it and its good, still howls, looks like a new rear end for me but i planed on it any way, 4 wheel parts has a deal, auburn posi, new ring and pinion, and master install kit $579. i think i might go with that and have a local shop install it.
thanks for the advice