What fluid for rear diff

[littleredstroker]

Hope this is in the right place, gonna change fluids in my rear end and am not sure what to go with, I don't really care to go to a synthetic unless someone can sell me on why, and I don't want to order anything online, the cover is leaking and I need to do it tomorrow.
Also, just use rtv on the cover? Or what

autocorrected by taptalk

 

[PatriotHauling]

Hope this is in the right place, gonna change fluids in my rear end and am not sure what to go with, I don't really care to go to a synthetic unless someone can sell me on why, and I don't want to order anything online, the cover is leaking and I need to do it tomorrow.
Also, just use rtv on the cover? Or what

autocorrected by taptalk

75w140. You MUST use a synthetic, Ford says so. If you have a limited slip you will need an oil with the LS additive (it will be clearly labeled) or get some off the shelf, best to get that from Ford.

Most good gear oils will have the LS additive.

Yes, RTV is used on the cover.

 

[littleredstroker]

Feel totally stupid here.... How do I know if its limited slip?

autocorrected by taptalk

 

[PatriotHauling]

Look at the tag on the differential. It will say (in code)

 

[littleredstroker]

Ok so 70-140 synthetic with ls additive gotcha. I know this truck came.from.michigan and the tag is pretty rusted off...

autocorrected by taptalk

 

[littleredstroker]

75*

autocorrected by taptalk

 

[PatriotHauling]

You can check your door tag too. Under AXLE is a 2 digit code.

Axle Type
31 — 3.73 non-limited slip, F-250/Excursion
C1 — 3.73 limited slip, F-250/Excursion
32 — 4.10 non-limited slip, F-250
C2 — 4.10 limited slip, F-250/Excursion
33 — 4.30 non-limited slip, F-250
C3 — 4.30 limited slip, F-250/Excursion
36 — 4.56 non-limited slip, F-250
C6 — 4.56 limited slip, F-250

 

[littleredstroker]

Thanks

autocorrected by taptalk