Does anybody use Mobil 1 75w 90 in place of the Motorcraft 80w 90 in the front diff? Also, if it is an acceptable substitute, would you use Mobil 1 75w 90 or 75w 140 in the rear (8.8 LS 4:10 gears)?

 

ttt

 

The mobil-1 75W90 would be the better of the (2) choices for any ranger. Much better than the motorcraft product. You may also want to consider looking into the Amsoil severe gear 75W90. Either way, both are much better than the motorcraft gearlube.