Need help with rear end id

[Grandpa54]

I just bought a 66 chevy panel the sheet on the glove box door says it has a 3.73 posi. I would like to varify that ,the code on the axle tube is hc123ow
d

mark

[Lowl!f3]

pull the rear pan off. if you see springs and stuff in the carrier. it will be a posi. if not, then its an open carrier just a 373 like mine.

[Captainfab]

It should be a posi, but you know most anything can happen in 48 years. The best thing to do is pull the rear cover and have a look. The oil more than likely needs changed anyway. The differential is one of the most neglected parts of a vehicle. For some reason most people seem to be afraid to pull the cover and change the gear oil. It is very simple and will only cost you a couple quarts of gear oil, posi additive if applicable, and a cover gasket. In exchange for that you will know exactly what is in your differential, the condition of it and the satisfaction of knowing it has fresh gear oil and will be good for a couple years, depending on how much you drive it.