Super 8.8 Gear oil?

[jridout325]

Going to be changing my rear diff fluid out soon and debating which fluid to go with. Manual calls for 75w-85 I think that's pretty thin. I'm debating between valvoline 75w-90 or 75w-140. The reason I'm thinking about 75w-140 is because it should offer better protection and it is what ford used for years until they switched to 75w-85 likely due to slight mpg gain. Just seeing if anyone has used 75w-140 in these.

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[Eighthtry]

Having zero experience in this matter qualifies me to throw an opinion out there.

1. How will you be using this truck?

2. Is the gear oil synthetic?

I like the thought of more protection offered by the 75-90, but would not run the 140 unless you are really thrashing that rear end. Heavy towing, bed loads, high summer temperatures, drag racing, parade floats?

If you really live in Iowa and are rarely towing or thrashing, then I would leave your rear end alone until you are 50-75,000 miles down the road, then change it to 90. Using only synthetic. Then change every 100,000 miles thereafter.

 

[roadPilot]

Either will be fine. Using lighter weight diff oils will theoretically give you better fuel mileage but likely nothing you'll see real world.

I used Valvoline full synthetic 75W-90 in my 2021 F150 Super 8.8. I use the "flex fill" bags, not the hard plastic quarts bottles. Best prices @ rockauto.com usually.

IMHO, waiting until 75K to 100K miles is ridiculous. Ideally, I like to change trans fluid, transfer case, and diff oils every 35K or so. Installing aftermarket trans pans and rear diff cover with drain plugs makes that a snap (after the first time), as you don't have to remove the pan/cover. Can't really do that on the front diff, as you'd have to pull steering and all kinds of other stuff to get the cover off, so just use a hand pump to exchange the oil

 

[jhelrey]

Go to Amsoil and they have specs on what you should use for weights, etc.

 

[JCsTruck]

change your differential oil every 30,000 miles despite what the owners manuel says, or you will be dealing with a pinion bearing failure, especially if you tow or drive a lot in a hot climate. I speak from experience.

 

[FaaWrenchBndr]

change your differential oil every 30,000 miles despite what the owners manuel says, or you will be dealing with a pinion bearing failure, especially if you tow or drive a lot in a hot climate. I speak from experience.

I agree

 

[FaaWrenchBndr]

Going to be changing my rear diff fluid out soon and debating which fluid to go with. Manual calls for 75w-85 I think that's pretty thin. I'm debating between valvoline 75w-90 or 75w-140. The reason I'm thinking about 75w-140 is because it should offer better protection and it is what ford used for years until they switched to 75w-85 likely due to slight mpg gain. Just seeing if anyone has used 75w-140 in these.

what state do you live in?
75w140 would be fine for summer use or if you live in a sourhern state.
It would be a bad option for use in the winter if you live in Minnesota

 

[jridout325]

what state do you live in?
75w140 would be fine for summer use or if you live in a sourhern state.
It would be a bad option for use in the winter if you live in Minnesota

I am in Iowa. I ended up going with 75-90

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