67 Deville rear end fluid change question

[jims427400]

I have a 67 Deville and I want to drain and refill but am unsure if it has positraction. Do you all refill with 80/90 and a couple bottles of GM posi fluid?

Jim

[chrisntam]

I changed the diff fluid in my '70 this spring, it was not posi, I've attached a pic of an "open" differential.  The posi unit will have a more solid center carrier with some springs, IIRC.

If not posi, just use normal 80w90.  If posi, I "think" some gear oils come ready to go for posi units.

Check to see what the local parts stores have to be sure they have both types before you take it apart.  Mine took a little less than 3 quarts, IIRC.