Differential fluid change - do I need friction modifier?

[Ruger]

Gang, is there any particular reason to favor one synthetic gear oil over another? Mobil 1 vs. Royal Purple vs. Amsoil vs. Castrol?

 

[Mil T]

MCR, there's a few valid points answered on your question, more fluid will take longer to over heat, but also a little longer to cool, but being an aluminum fined cover should aid in its heating and cooling, being able to check and fill easily, for the guys that would see deep water , being able to drop the fluid on sight, and not worrying about losing diff cover bolts in the dirt, but I would also be the person dropping the cover and pulling the axles when I got home, just to make sure all water was out of the rear and axle tubes, then you also will have the hand full that do it, because every one else is doing it ( oooh aaah) factor, as for the AFE and G-2 covers I cant speak for there strength or how thick the covers are, but in my case I chose a cover that is pretty dame close to bullet proof, doesn't protrude as much as the others, has the easy fill and drain, but also gives me support on my diff bearings, granted you won't launch your truck and hook like a car, but there is always a load factor no matter, so for 200, I feel I got the best of both worlds. Link to my cover bellow, also Nitro gear and pinion make the cover also. And I forgot to add, I also used the ARP STUD KIT.

Ford Girdles, Ford Lightning 9.75" Rear End Girdle, TA_1804 | TAPerformance.com

Ditto this cover. I've had it on for about a year. Comfort in knowing it's sturdy for my type of abuse. I also like the bearing preload bolts. Easy install.

---------- Post added at 08:03 PM ---------- Previous post was at 08:01 PM ----------

Gang, is there any particular reason to favor one synthetic gear oil over another? Mobil 1 vs. Royal Purple vs. Amsoil vs. Castrol?

No. Only what your pocket book dictates and what color bottle you like. I have run Mobil 1 for so long I don't know anything else and I've never had any issues with lubrication on anything. I read a review a long time ago about oils and Mobil 1 has always been a top of the heap lubrication.
Mil T

 

[Ruger]

Mil T, that's also what I read about motor oil - that Mobil 1 is tops. I haven't used any other motor oil for decades. But I haven't read that about gear oil.

 

[Vash]

Changed the front diff oil yesterday. Used Amsoil Severe Gear 75w-90 because it's listed as a replacement/substitute for 80w-90 and I wanted to stick with the Severe Gear series of oils for both diffs. The manuals etc. that I read said about 1.8 quarts, but oil started weeping from the fill hole a bit before then so I stopped there. I may check it after driving a bit, but both diffs should be good to go. Now, to save up for the crapload of fluid required to flush the transmission at the dealership.

On another note, the slightly lighter front diff oil didn't smell nearly as horrible as the rear diff oil. I also wish the front had a drain plug or aftermarket cover option, but there's definitely NO extra room up front with the steering components in the way.

Also, I sealed things back up using Permatex Right Stuff and put a little PTFE thread sealer on the fill plug.

 

[R1jamn]

2014 Raptor Owner here.
I read thru this whole thread, then checked my manuals.
Definitely some ambiguity between the two manuals.

My 2014 F150 Owners Manual (Capacities and Specifications) PG. 301
clearly states to use 75w-140 synthetic rear axle lubricant.
Note #5 (Add 4 fl oz. of "Additive Friction Modifier" for complete fill of 8.8-inch Traction-Lok axles.)


My 2014 F150 SVT Raptor Supplement Manual (Capacities and Specifications) PG. 31
clearly states to use 75w-85 premium synthetic hypoid gear lubricant for the rear axle.
Note #5 (Do not add Additive Friction Modifier to the rear axle.)

Question for Crystal.

Is the 2014 F150 Raptor Supplement Manual correct?
What oil is placed in the rear differential of the 2014 Raptor from Ford?

I do not like to assume anything.

 

[R1jamn]

I just ordered an oil analysis kit from Blackstone Labs.
I'll send in a sample and find out exactly what the viscosity is in the rear diff of my 2014 Raptor. I submitted a note asking if they could determine if there is a Friction Modifier in it also.

I'll keep everybody posted.

 

[Red]

No modifier needed in the newer rear axles.

 

[Vash]

Traction-Lok is Ford's name for their limited slip differential that uses clutch discs. You DO NOT have this rear differential if you own a Raptor. You have an electronic locking rear differential. Also, correct me if I'm wrong, but you have a 9.75 axle and not an 8.8.

 

[J DAMAGE]

Hey, Ruger!

Just heard back. Here's the message I received after I sent your questions up the chain:

"There is no change in the axle assembly. It should still be using the 75W-140 axle fluid, 2010-2014. Friction modifier is not needed because it is an ELD (Electronic Locking Differential). The Owner’s Manual does not specify that, but friction modifier is only needed on limited slip non-ELD axles."

Crystal

Here's a past post on this topic.

 

[R1jamn]

Traction-Lok is Ford's name for their limited slip differential that uses clutch discs. You DO NOT have this rear differential if you own a Raptor. You have an electronic locking rear differential.

Thanks for the info.

I'll wait for the oil analysis from Blackstone labs to verify what Ford Motor Company used for the rear diff oil in my '14 Raptor.

---------- Post added at 06:00 PM ---------- Previous post was at 05:55 PM ----------

Here's a past post on this topic.

Thanks J
The Ford F150 SVT Raptor Supplement still contradicts this info from Crystal.

---------- Post added at 06:21 PM ---------- Previous post was at 06:00 PM ----------

Also, correct me if I'm wrong, but you have a 9.75 axle and not an 8.8.

Yes, 9.75 with a 12 bolt rear diff cover.