When in doubt, go for the best you can get.... let's not forget the manuals are proof read and printed by proof readers and printers..... CD manuals get a lot of cut and paste and it is assumed that we can muster common sense (no, this is not an insult).
75W140 is synthetic..... excellent cold flow characteristics, excellent shear resistance - and it is in your owners manual...... a much better source for this than the WSM (work shop manual). The WSM shines when it comes to procedures but even then there are typos and such.....We exclusively use 75W140 in these rear diffs in our dealership.....
HTH
Jim Warman snipped-for-privacy@telusplanet.net
rear differential lube? My Ford repair CD says 2 things, one is 80w90 for standard models, and the other is 75w140 for towing packages and V8 models. However, my owners manual says 75w140. I'd like to run the lighter weight oil for better fuel economy, but I don't want to damage the differential. Thanks.
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