The Stovebolt Site Forums The Parking Lot Tons 'o Fun rear end oil

Anybody know what the best grade of oil to use in the stock rear end on a 59 3800, and how much to put in??

sae. 85-90 is what i use in my rears.

what about the transmission?

I'm most likely looking at filling both my rear end and transmission with synthetic when I get it all back together. Just curious if you guys are using the same weight in the 4 speed tranny as the rear end as well as what the collective thoughts are on synthetic.

I run 85-90 in both. I believe I added some Lucas oil treatment to the tranny. Couldn't tell you if anything feels different or "smoother"

As Workmaster says, 80/90 works for both. Fill till it starts to run out of the fill hole. If you go with synthetic, which will keep the heat down on the hot days and flow better on the cold ones, you will probably end up using a 75/90.