rear differential fluid: what to use?

[NisAznMonk]

Howdy!

I have a 2004 Sport Trac XLT 2wd with a 3.73 non-LSD rear differential. I'm getting conflicting information in my search results on what kind of fluid to use.

Has anyone used 80w-90 in their rear differential? I found that weight here: http://www.mysporttrac.com/mysporttrac/projects/TrickFlow/Installing a Trick Flow 8.htm

Or am I supposed to use synthetic 75w-140 without the friction modifier? http://www.explorerforum.com/forums/showthread.php?t=294758&highlight=differential+fluid

There isn't a tag on my differential cover, and the door sticker has an axle code of 46.

 

[1998Explodasport]

It should be 80w-90 unless you have the LSD which you don't. Same with the front.

 

[scucci]

It's in the owners manual-get a pdf version here:
Dead Link Removed

Rear axle lubricant:

Motorcraft SAE 75W-90 Fuel
Efficient High Performance Synthetic Rear
Axle Lubricant

Conventional
Axle 1.7L (3.5 pints)

Limited slip axle 4 1.5L (3.25 pints)
Limited Slip differentials must add 118ml (4 oz) of Additive Friction
Modifier XL-7 or equivalent to the rear axle whenever the axle has been
serviced.