said by guhuna:Easiest would be to jack the rear up and take he pumpkin cover off to do a visual inspection.
You could pull the rubber plug but since its got all those miles on it might as well take the cover off and check it out.
Removed the cover, oil was rather low, but the gears looked fine to me.
Changed gasket, there was a break and leak in the old gasket at the top right, added oil (2qt Lucas 85w-140 plus 1qt Lucas Heavy Duty Oil Stabilizer), took it for a test drive.
Started by testing reverse, it worked, drove to a local gas station and when it downshifts from what I think is 3rd to 2nd going from 35mph to 25mph, I start to here clanking around and like I am dragging something metal. Slow it down to 20mph the rest of the way and stopped at the gas station.
Started it back up, tried reverse and it worked, drove back to the house and the same started to happen when getting up to 35 and going back down to ~25mph. I stopped, shift down to 2nd and drove home without an issue.
Texted with my mechanic bud, he still doesn't think it's the transmission, as it shouldn't whine, clank, or grind, but the drive shaft or the rear diff and asked me to check the drive shaft to see if it spins by hand or has play in it.
I'll have to do that today after work.
Thanks much for your help!
--edit--
Spoke with another IT coworker and he, despite all others, think that I maybe missing teeth on the 3rd or 4th gear. Just tossing that out there.