Hey,
I have a 68 dodge charger w/a 383 4bbl. 727 TCI 3 sp on colum auto trans..... motor,trans,converter,wiring harness and everything is new in engine bay..., 2.76 open differential. havent checked the fluid but the casing temp on bottom was 140 degrees after a 20 min drive at 70mph on interste also having a vibration like a trans mount when car is turning a certin way but mount is new and bolted on properly. Is the diff temp normal or could it be bad in the cense of axle berrings or gears?

what type of fluid would be the best to put in if i drain it?

Thanks

 

I've been following your dilema and looking at the rear is a good idea. I would unbolt the driveshaft and "feel" back and forth on the yoke, should have very little play. Raise both wheels and turn many times bothways to see how smooth. Then do the same while holding each of the wheels so the other wheel turns, this will allow you to "feel" the spider gears in the differential. If it is an 8 3/4" take a bendy magnet into the drain plug hole and fish around. Fill with 80-90W gear lube, depending on your local outdoor temp, 90 hot, 80 not so hot.

 

When was the last time the ale had been serviced? What rear axle is it? Is it an open case or Sure Grip? What speed do you feel the vibration at? Is it only while turning? 140*F for an axle temps is not too bad. If the vibration is coming from the axle, that will mean that something is bent.