Ok boys and girls, I think I've got a problem building up here. I'm pretty sure I've narrowed the sound down to comming from the back end. I running an automatic 4l30e tranny in my 96' Rodeo and lately I've noticed an increasing grinding/ringing sound coming from the rear. It occurs whether I'm in neutral, reverse or forward and most obviously when I'm accelerating or decelerating against the engine. In otherwords, it's most noticeable when I'm not coasting at a constant speed but still there barely noticeable when I am. Basically the sound is more prevelent when there is pressure on the drive train in one way or the other, and the sound gets progressively higher pitched the faster I am going, not engine rpm dependent. I'm pretty sure that it's got to be something in the diff at this point as I took it to a local lube place as soon as I heard it and had the fluid level checked. Don't kill me for this one guys, I know I should have probably checked it more often, but the diff was bone dry. Don't know if this happened as a result of poor workmanship from the last time I requested lube all the way around, or if I might have a crack, the latter seems unlikely. Anyway, IIRC I've got a D44 diff and was wanting to throw in some sort of locker anyway. Would anyone guess that I will need to replace anything other than what I would get if I went to either a locking diff or a PosiTrac system, like pinion and ring gear possibly? Is it possible that the sound could be comming from a u-joint instead? Any help would be appreciated. Thanks.