i have been using synthetic oils in my differentials , engines , transmissions since the early 90's in every vehicle i've owned and still own ( 1977 F150 , 1972 Mustang ,) and the wife's Liberty , Grand Cherokee , Dodge Caravans etc. she's owned including lawn mowers and snow blowers and have had zero problems -- i have a problem with the previous post statement " not to break in gears with synthetic oil " so could someone please explain to me why ALL the auto companies have been using synthetic oil in their differentials since the late 90's if not earlier . look under that Ram , F150 , GMC , and rear drive cars such as Mustangs etc. and the tag on the diff will say use synthetic oil only usually in the 75-140 weight , i am sure they did not break in the diffs with dino oil then changed it out to synthetic before shipping the vehicle .
