I am wondering what type and weight of oil to put in the rear diff. I have a 1967 f100 with a 352 and 4 on the floor. There is no power or performance upgrades on my truck. I seem to find allot of info for gear oil type for trucks that are used for racing and/or the track, but nothing for an occasionally driven truck. I don't hot rod or abuse my truck when I'm driving. The oil that is in there now is ultra thick, almost more like a grease than an oil. What does ford reccomend?

 

I use 70W-90 for my daily

 

I use 85-90w. If it it a limited slip don't forget the friction modifier.

 

You'll need 5 pints of gear oil to fill the rear end. This will require buying 3 bottles of gear oil.

IF you have a limited slip differential, you'll need 4oz of friction modifier. Pour the friction modifier in first followed by the gear oil until the oil just starts to run out the fill port on the 3rd member.

If you have an open (single track) differential, the friction modifier will not be required.

 

Ford Motorcraft 80W/90 Premium rear axle lubricant.
Part number XY80W90QL for quarts.
Covers specification numbers WSP-M2C197A, GL5, MT-1


.
************
Ford Motorcraft Friction Modifier Additive.
Part Number XL-3. Spec number EST-M2C118-A.
4 oz bottle..

 

80W-90 gear oil as mentioned. Any kind will work.

If there's a lot of miles on the truck, you could jump up to 140 weight. I run the thick stuff simply because I fall under "severe service"