Diff lube confusion in owner's manual

[JohnnyO]

I have a 2005 Sport Trac with a factory limited-slip rear. I'm going to change the lube in the diffs (already did the front...I off-road some) but in the manual on the Capacities page it calls for synthetic 75w-90 for the rear and on the Specifications page it calls for synthetic 75w-140. This is a separate listing than the front axle.
I already bought M1 75w-140, I guess I'd rather err on the side of high viscosity here, but what do y'all think?

 

[Whimsey]

If that's the truck version of the Explorer then it uses 75W-140 in the rear diff. The same as the Explorer.

Whimsey

 

[1 FMF]

proof the right hand doesn't know what the left hand is doing (writing).

Hasn't ford gone to fill for life for axle fluids? I think their only gear oil is motorcraft 75w-140 synthetic, it would stand to reason a fill for life fluid would be the higher viscosity synthetic vs. a 75w-90. I wonder if the fuel economy 5w-20 nuts know what the rear axle guys are using?

my thoughts- it don't matter.

 

[montero91]

better make sure whether to add the friction modifier because my ford lsd requires it and without it you will get a vibration from the rear end that will keep you up at night.

 

[JohnnyO]

quote:

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Originally posted by 1 FMF:
Hasn't ford gone to fill for life for axle fluids? I think their only gear oil is motorcraft 75w-140 synthetic

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Not when you go off-roading and drive it under water, no.

The description for the 75w-90 says Motorcraft Synthetic High Milage Axle Lubricant or some such, I don't have it in front of me right now.

 

[Kestas]

Doesn't the rule of thumb apply here, where you use 75W-90 for daily driving and 75W-140 if you expect to do a lot of towing?

JohnnyO, this wouldn't be the first time I've seen Ford goof in their published maintenance requirements. Do what makes most sense to you.

 

[Jimbo]

Older Ford 4x4 light trucks called for 75W-90 for the Dana front axles and 80W-90 or 75W-140 in the Ford rear axles.