Newby seeking critique of plan to take 2018 F-150 differentials to 250,00

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119
Location
MA
Hi All, A newby seeking some advice. I'm trying to green-light a list of (3) or so "good to great" (but does not have to be "best") differential fluids for my 2018 F-150 diff fluid selection. My F150 is unladen 90% of its life and 10% of the time at 14,000 lbs gross combined weight (i.e., towing 9000 lbs). I want my plan to have a reasonable chance of bringing my differentials to 250,000 miles. Notes: The official spec for both front and rear is "Motorcraft® SAE 75W-85 Premium Synthetic Hypoid Gear Lubricant XY-75W85-QL with specification WSS-M2C942-A", but the issue is that 75W-85 is hard to find and Ford's offering is expensive at $25/quart on amazon. My F150 has calls for Hypoid gear lubricant, has a rear electronic locker, and so far as I know, does not ask for friction modifiers since it lacks a limited slip design. My plan:
  • A 75W-85 or 75W-90 full synthetic that meets or exceeds GL-5
  • Replace said fluid every 75000 miles
My tentative list of green-lighted fluids:
 
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kehyler

Thread starter
Messages
119
Location
MA
Originally Posted by demarpaint
I made it real simple for myself. Mobil 1 in the front and rear differentials in both my Jeeps.
Is your choice transferable to my truck with its specific use-case?
 
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35,809
Location
NY
Originally Posted by kehyler
Originally Posted by demarpaint
I made it real simple for myself. Mobil 1 in the front and rear differentials in both my Jeeps.
Is your choice transferable to my truck with its specific use-case?
That's what I'd be using if I owned your truck. wink
 
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200
Location
Memphis TN
I just changed the oil in my F150 at 70K I used Royal Purples 75/90,I dont tow but if I did I would use a thicker oil All the brands mentioned are great products
 
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2,413
Location
South Carolina
M1 also has a limited slip additive. Mobil1 75w-90LS: LS stands for limited slip (ready). Good luck finding a 75w-85 on the isles of WM. M1 would be a good choice. I ran it for 30 years but recently changed to SuperTech syn 75w-140 and I like it. Your axles should easily reach 250k with any GL5 oil.
 
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3,275
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On another site
Amsoil make fantastic gear oils, as does Schaeffer. The ones listed are very good as well. [censored], any one of them will fit your plan and your diffs will go beyond 250k miles.
 
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1,005
Location
Alberta
Ford spec'd 75w140 for the last 20+ years in the rear diff until the 2015 model year . No mechanical changes in the 9.75" axle, if that's what your truck has. If you tow 9000lbs, I would suggest consideration of something that has been proven over that time period and not influenced by EPA mileage requirements. https://www.redlineoil.com/75w140-gl-5-gear-oil https://www.fcsdchemicalsandlubricants.com/Main/product.asp?product=SAE+75W%2D140+Synthetic+Rear+Axle+Lubricant&category=Transaxle%20Fluid
 
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9,103
Location
Houston, TX
If it were mine, I would be running Amsoil 75W-110 in the front axle because 75W-110 is the upper viscosity that 75W-90 used to be before the J306 tables were updated. I would run Amsoil 75W-140 in the rear because until Ford seemingly caved into CAFE, 75W-140 was the viscosity in those axles for decades. Change the oil early (less than 15K miles) because the vast majority of wear occurs early in an axle's life, not later or over time (UOAs back this up, it is not an assumption). After the initial change at 15K or less, I would set my OCI to 100K mile intervals even when towing, because I towed between 8K-9K pounds (fifth wheel trailer) for 45% of 160K miles on my 2010 FX4 and I did not see any advantage to changing it sooner. Your ELD does not need friction modifier and the Amsoil will be good to go out of the bottle in both axles. [Linked Image]
 
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6,235
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Kalifornia Kollective
First off the enemy of diff's towing is heat. So I would look for a rear cover in cast aluminum that also increased the oil capacity. Second I would install magnetic drain and fill plugs. Get as many micro fine steel particles out of there as possible as soon as possible. I have never gotten over 150K out of a Ford rear end before it needs service, but I may beat on mine harder than you do ... Usually not new gears, but a pinion lash reset to stop whine. And that often means new pinion bearings and a seal. No biggie, but it needs doing when it comes up. I'd run Red Line if looking to get away from Motorcraft laugh
 
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4,563
Location
N.C.
I changed my GM G80 locker a month ago and used the Mobil Delvac 1 75w90 full synthetic with no LS additive. A gallon cost me $51.75 shipped from Amazon. It looks like the Delvac 1 might be good for your application as well.
 
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2,578
Location
GoVols
Originally Posted by BrocLuno
First off the enemy of diff's towing is heat. So I would look for a rear cover in cast aluminum that also increased the oil capacity. Second I would install magnetic drain and fill plugs. Get as many micro fine steel particles out of there as possible as soon as possible. I have never gotten over 150K out of a Ford rear end before it needs service, but I may beat on mine harder than you do ... Usually not new gears, but a pinion lash reset to stop whine. And that often means new pinion bearings and a seal. No biggie, but it needs doing when it comes up. I'd run Red Line if looking to get away from Motorcraft laugh
How often did you service the rear gear in the first 150K miles ??
 
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5,016
Location
Southeast
Well, the front diff doesn't even spin unless 4wd is engaged - as this board recently helped me see, it has vacuum-driven disconnects in both front wheel hubs. So the attention must be on the rear. There's some debate on the aftermarket diff covers. Those with a squared inner profile apparently don't flow the fluid in circulation out to the axle bearings, so be aware of that caveat. The only times I've truly heated up a diff to a crazy amount was towing near max capacity on mountain roads, besides that it hasn't been much of a thing. I do not consider 160F at the differential to be an issue. 200F and I'd start asking questions, such as, am I driving it too hard? There's been some talk here before stating that a 90W is all a diff should ever need in a passenger vehicle or half-ton, and that any weight above that is to be looked at skeptically, such as a factory band-aid for poor axles (looking at you jeep WK). I'm not aware of Ford axles having any build issues. Having never been able to collect better data on my own via instrumentation or taking the time to do UOAs of differential fluids, I either stick with factory recommendations or Amsoil's 110 weight for a little peace of mind without going whole bore into 140 territory.
 
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