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- Sep 26, 2010
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I disagree, but am fine to do that based upon my experience--which is towing 8-9K pounds through all terrains and in temperatures up to 117°F. It depends on load, ambient temperatures, and other factors. Had Ford substantially changed the bearing or shaft sizes prior to the reduction, I would agree, but they did not--the axle is EXACTLY the same, just thinner oil was specified.75w140 is almost certainly overkill in a half-ton differential.
Dana specified 75W-140 in my Dana 44 axles under my Wrangler and FCA specified 75W-90. There is only one reason an OEM would reduce viscosity and longevity of the axle is not it.
Oh, and Richard Petty can afford to rebuild his axles every day if he so chose, I, on the other hand would rather not...
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