Problems with 1961 rear differential...need advice

[Captainfab]

There is a thread on here that has the rear differential codes and what they are. I believe you can find it in the '60-'66 FAQ Index. The HC is the code.

Edit: I found the thread here: http://67-72chevytrucks.com/vboard/s...d.php?t=327764

Looks like you have a '65-'67 3.73 posi rear differential. Of course this is assuming nothing has been changed in the last 40+ years. I'd pull the cover and have a look. More than likely the oil needs changed anyway. It'ss just cost you a couple quarts of gear oil, a bottly of friction modifier and a cover gasket. Then you will know for certain what gears you have, and the peace of mind knowing you just serviced your differential, and all is good inside.