Differential fluid change - do I need friction modifier?

[pastorwug]

The top hole is used for a cooling system.

https://performanceparts.ford.com/part/M-4000-M8S

https://www.maximummotorsports.com/MM-Cobra-IRS-Differential-Cooler-Kit-P1077.aspx

That helps, thanks!

 

[HotLap]

That helps, thanks!

What? Hey MTF neither of your links are the Ford Performance Diff cover I installed on my 2018 Raptor. And per FP the upper fill hole is to be used only if you have lifted your truck as the rear diff is now at an angle (driveshaft tilts upwards) so to get the right amount of fluid you use the upper hole. If the truck is NOT lifted, you will have too much fluid if you use the upper fill hole. Perhaps I'm misunderstanding Pastorwug's question??

Good luck...

 

[MTF]

What? Hey MTF neither of your links are the Ford Performance Diff cover I installed on my 2018 Raptor. And per FP the upper fill hole is to be used only if you have lifted your truck as the rear diff is now at an angle (driveshaft tilts upwards) so to get the right amount of fluid you use the upper hole. If the truck is NOT lifted, you will have too much fluid if you use the upper fill hole. Perhaps I'm misunderstanding Pastorwug's question??

Good luck...

Ummm... I was just showing what the top hole is for.

Lifting the truck doesn't change the angle the of the rear end, only the driveshaft.
You can change the angle of the rear end if the driveshaft angle is too great.
Then you would add a wedge shim to angle the rear upwards to minimize u-joint binding.

 

[RapidRedGEN2DFW]

I just changed my rear diff fluid and diff cover for the first time. I went with Amsoil 75w110 and Ford Performance diff cover. Amsoil states no friction modifier needs to be added to their gear oil.

 

[pastorwug]

My truck is not lifted and I use the lower hole to fill to.
Just changed my diff oil after 30k miles, everything looked good.
Went with syn gear oil.

 

[gimmethattruck]

Get some for me too while you're there.

 

[marioec]

This thread is so confusing everyone has different opinions on using friction modifier lol
I have a 2014 and getting ready to change the front and rear differential fluid.

Simple question YES or NO

2014 SVT Raptor with torsen front differential using Amsoil

Using :
Front Differential Amsoil Severe Gear 80W-90 with or without Friction modifier ?

Rear Differential Amsoil Severe Gear 75W-140 with or without Friction modifier ?

 

[Chris@FreedomMotorsports]

This thread is so confusing everyone has different opinions on using friction modifier lol
I have a 2014 and getting ready to change the front and rear differential fluid.

Simple question YES or NO

2014 SVT Raptor with torsen front differential using Amsoil

Using :
Front Differential Amsoil Severe Gear 80W-90 with or without Friction modifier ?

Rear Differential Amsoil Severe Gear 75W-140 with or without Friction modifier ?

With Amsoil gear lube, you don't HAVE to use friction modifier in the front, because Amsoil gear lube already has friction modifier in it. Ford does recommend friction modifier in the front, so if it makes you feel better to follow their recommendation on that, use THIS ADDITIVE with your Amsoil Severe Gear. The rear diff doesn't get friction modifier at all, aside from what is already formulated into the Amsoil gear lube.