2012 Mustang V6, 75w-140?

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Looking up the specs for the rear end in my wife's 2012 Mustang V6, it says it takes 75w-140. Why? I could understand it in a 9" rear in a truck that'll see heavy duty use, but an 8.8" with 2.73 gear behind a V6 pony car? Any reason a high end 75w-110, such as HPL Diff Life 75w-110, wouldn't work in that rear end? I know there was some controversy over this, but haven't really dug into why.
 
Ford changed the spec a long time ago for 75W140. My 2002 is spec for it too. Ford was having issues with 90 weight gear oil and spec the 140. No issues with the 140.
 
What were the issues though? I know about the change over, but never heard a reason why. Was it a broad issue across all many rear ends or just certain circumstances in which Ford changed to 75w-140 as just a CYA.
 
I run 75W-140 syn gear lube in my Toyota Tacomas and Ford p/u rear ends. I couldn't tell any difference , but we used 85W-140 at work so I took enough for a rear end and 3 on the tree trans change decades ago in my ford F150 with a 300 ci 6 cyl ,I really could tell the difference because the 85W-140 is much thicker.
 
That spec was instituted before the new formulation 75W110 was developed.

Again, 75W110 is a good all around grade for any differential.
 
Originally Posted by MolaKule
That spec was instituted before the new formulation 75W110 was developed.

Again, 75W110 is a good all around grade for any differential.


This is what I was curious about. Thanks for confirming that.
 
Originally Posted by FastLane
Ford changed the spec a long time ago for 75W140. My 2002 is spec for it too. Ford was having issues with 90 weight gear oil and spec the 140. No issues with the 140.

Until 2015 in most of the vehicles that have a 9.75 or 8.8 axle they reduced it to either 85W-90 (conventional) or 75W-85 (synthetic). All rationale points to CAFE since no changes that have been announced took place within the design of the axles.
 
Some things don't make sense. My Charger SXT 3.6/8 speed and Challenger R/T 5.7/6 speed takes 75W85, so does the all mighty HellCat. My 2018 RAM 1500 short bed 2wd 3.6/8speed takes 75W140. But yet a 3/4 ton or 1 ton RAM takes 75W90. ???????
When somebody can figure all this out let us know.
 
It was years ago but the Ford dealer printed out the change to 75W140. The switch solved the 8.8 issues. I'm curious what would have changed to go back to the thinner gear oil.

I have nearly 200,000 kms on my Mustang now. I just changed the limited slip clutches to the carbon fiber version. Other than that it's been great. Still quiet. The car has seen "high" speeds too.
 
I just did my 98GT rear end this past weekend. Used UltraLub 75w90 full syn and 4oz of Lubeguard friction modifier.
 
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