anyone do there Differential lately?

[lineman76]

This is what people are saying to use, any good? also this might seem stupid but how would a person till if they had 10.5 diff? Ford specifies 75W-140 SYNTHETIC ONLY for the Sterling 10.5 differential along with 4 oz of XL-3 modifier
thanks

[JSchuricht]

You know you have a 10.5 if you have a 99+ truck or swapped in a axle from one. The OBS trucks have a 10.25. For a flush, remove all but the top two bolts on the cover, loosten the top two and slip a puddy knife between the cover and case. Drain oil, remove cover, clean up RTV, apply new RTV, wait for it to cure, pull the fill plug and fill till it starts coming out the hole. Drive it a bit in tight circles, if the wheels start to chirp, add some friction modifier. It's also a good excuse to install a 08 aluminum cover if your old one is rusty like mine was.

[lineman76]

thanks i got a 93 and i been doing a little reading and from what i understand is i could just put in any old Rear Axle Gear Oil. does that sound right?

[JSchuricht]

Just need to make sure it's gear oil, the correct weight and synthetic.