Ford 9.75" Differential Gear Lube Change

[josephp732]

I have a 2015 Ford Expedition with the heavy duty towing package, 9,800lb towing limit, the SUV with came with Ford's 9.75" rear differential.
It's time to do my first set of full fluid changes (30k miles) and my manual shows the rear gear oil to be 75W-90.
I tow a ~7,500lb boat/trailer from NJ to FL 4 times a year and push very close to the total GVWR with all the people and stuff in the truck.
Should I just change the gear oil out with the same Motorcraft 75W-90? Is there any value in going to a heaver weight oil like a 75W-140?

 

[Inspecktor]

75W-90 is fine. If you want a little more peace of mind, 75W-110 or 75W-140 will work as well. My Dakota requires 75W-140 for towing or hauling heavy loads. Amsoil Severe Gear in any of those grades will work very well for you.

 

[CT8]

75W-140

 

[dogememe]

Amsoil 75w-110

 

[buck91]

Interesting. Same dif I have in my F150 which is spec'd for 75w140. They did this with the 8.8's, too. I'm sure 75w90 is fine if you don't tow hard. Might even net you 1mpg under certain conditions. That said, I run 75w140 in mine still.

 

[Oildudeny]

I ran 85-140 in my 98 f-150 which called for 75-140. no issues.

 

[hatt]

Heavy vehicle that is towing a lot, I'd go 75w-140 that F150s spec for sure.

 

[Snagglefoot]

Here you go.

 

[tcp71]

My 2016 f150 came with 75w90 in the diff. I changed it early with 75w140.

 

[josephp732]

Thank you all for the quick reply's - I placed my order for six quarts of Amsoil Severe Gear 75W-140.
I figured I would just use the same oil in the front differential also.

Here is a picture of a 2015 Expedition's 9.75 differential - it's an "interesting" design with mounting studs and a factory drain plug.
When mounted in the SUV the differential cover is only about 2 inches away from hitting the rear interdependent suspension arms.
So, you could never pull the cover off with-out taking off a lot of other parts.
Ford went to the 9.75 rear in this truck when they put the 3.5L V6 Ecoboost in as the only engine choice in 2015.