2004 Ford F-150 w/ 4.6L and 8.8" rear diff I was at the dealer today to buy some 75w-90 Motorcraft Synthetic Axle Lube as specified in my owners manual. The parts guy told me that all they have is 75w-140 synthetic and to just run that - he said that this is what Ford now specs for my diff in the service manual. I have found various brands of 75w-90 sythetic at parts stores in my area. I just thought I would run the motorcraft stuff since their fluids are usually top notch stuff. Is the 75w-140 motorcraft what I want to run even though this doesn't match my owners manual? or should I just use another brand of 75w-90 syn (Valvoline or the like). I am looking for others w/ experience running the Ford 8.8" rear end. What weight/brand have you had good luck with. Thanks Addition: I thought I should mention that the truck isn't used for heavy pulling or hauling. Mostly car like duty with the occasional 2 place ATV/Snow trailer behind it.