Differential Fluid Viscosity

[STLR FN]

Changing out the diff fluid, well actually changing axle seals and bearings. The owners manual says to replace with 85W-90, most everyone uses 75W-140, my FLAPS was outta 75W-140 and recommended 80W-90. Should I be OK? I did some searching and found that the 85W will thin no more than a 90W oil. Just wanna make sure I'll be OK up here in Mich. during the summer and winter months.

[STLR FN]

Nevermind I read the owners wrong. OEM calls for 80W90. I have the right fluid.

Thanks for the 15 or so people who took a gander but no replies.

[2003DOHC]

Nevermind I read the owners wrong. OEM calls for 80W90. I have the right fluid.

Thanks for the 15 or so people who took a gander but no replies.

The rear axle kits come with Motorcraft synthetic rear axle lubricant sae 75W-140. I would use this fluid. XY-75W140-QL

[thePunisher]

yep, dont use 80-90

[STLR FN]

yep, dont use 80-90
Why not????

[SamF]

Why not????

The upgraded Ford spec calls for 75-140 synthetic. I use Royal Purple, any brand high quality fluid will work.

[RF Overlord]

The rear axle kits come with Motorcraft synthetic rear axle lubricant sae 75W-140.


The upgraded Ford spec calls for 75-140 synthetic. I use Royal Purple, any brand high quality fluid will work.

^^^what they said^^^

[fastblackmerc]

I use 75-140 Redline with my 4.10's.

[STLR FN]

I went with the 75W140, I didn't feel comfortable with the 80W90. Thanks for the advice.

[whd507]

what about 85-140? I have that already.

[metroplex]

80W-90 and 85W-140 are usually non-synthetic.

75W-90 and 75W-140 are usually synthetic.

Ford used to specify 80W-90 for the 8.8" rear-ends, but have started to recommend 75W-140 across the board. Motorcraft 75W-140 is extremely overpriced at $16+ per quart (synthetic) but it is used as the factory fill in high performance cars like the S197 GT.