Gear Oil at 20,000 miles in Ford 9.75” Diff

[Panda87]

Hello again,
I ordered 6 quarts of HPL 75w-140 and a quart of HPL’s Differential Cleaner. I’m two weeks post shoulder surgery, spending too much time on the internet reading BITOG and buying HPL, lol.

I decided to drive around for a while then crawl under my ‘14 Navigator, crack the fill plug, pump out .45-.5qts of diff fluid and pump in the same volume of the HPL differential cleaner. As soon as I cracked the fill plug off, some lube started pouring out. The color of the lube was grayish when running thin against the diff housing and I thought “hmm, wonder if water got in?” so I drained the whole diff. I took a photo of what came out.

This was AMSOIL Severe Gear 75w-140 for ~20,000 miles, 5000 of which were towing a 7500lb camper. The differential fluid had likely never been changed prior to me draining it and filling with the SG, so I assume the SG picked a lot of the previous muck up from the old gear oil and held it in suspension. It was far darker than I expected and stunk like radioactive roadkill. My sons were playing outside and I heard one of them go “EWWW WHAT IS THAT SMELL!?” and made a vomiting sound.

I filled the diff with .5qts of HPL Diff cleaner, 1qt SG 75w-140, 1/2qt SG 75w-90 and 1qt of SG 80w-90. It was all leftovers from other changes and since it wasn’t going to be in there terribly long, I wasn’t worried about not going the full 75w-140. I’m at 163,500mi now on the Navigator and will likely run this to 170k, drain and refill with HPL 75w-140.

I’m not sure what to think of just how gnarly this fluid looks with only 20,000 on it. Maybe towing beat it up? Maybe it’s cleaned out remnants of the factory fill that was in for the first 140,000mi? What are y’all’s thoughts?

When I drain the Diff Cleaner and other fluids out at 170,000, I’ll take pics and add them to this post. Edit: I meant to add, there wasn’t an unusually different than normal amount of black paste on either the drain or fill plug magnets.

 

[SubieRubyRoo]

Sorry bud, but as good as those are individually I’d never mix HPL & Amsoil.

Also, why are you using 75w140? 75w90 HPL is more than enough… it’s used in the #43 NASCAR’s semi differentials… the thicker fluid is going to run hotter than thinner fluid, and remove less heat. That can actually cause more issues than what you were hoping to avoid.

 

[Panda87]

Sorry bud, but as good as those are individually I’d never mix HPL & Amsoil.

Also, why are you using 75w140? 75w90 HPL is more than enough… it’s used in the #43 NASCAR’s semi differentials… the thicker fluid is going to run hotter than thinner fluid, and remove less heat. That can actually cause more issues than what you were hoping to avoid.

Hey Subie! 75w-140 is the Ford recommended fluid for this vehicle and differential.

As for the mixing, it isn’t going to stay in there relatively long and the Ams 75w-140 was the only 140 gear oil quart I had. Now all I have left is some Royal Purple 75w-90. It’ll be in for only a few thousand miles. I won’t be towing much, if at all, while this brew is in there. For curiosity’s sake, why don’t you consider mixing brands a good idea?

 

[Passport1]

Agree changing the differential fluid is important. I'd just drain and fill with 75W-90 SuperTech. More importantly, shoulders sometimes need more time to recover from surgery. I had a torn labrum years ago and it was ~6 weeks until I'd do anything more than hoist a beer with that arm.

 

[Panda87]

Agree changing the differential fluid is important. I'd just drain and fill with 75W-90 SuperTech. More importantly, your shoulder needs more time to recover from surgery. I had a torn labrum years ago and it was ~6 weeks until I'd do anything more than hoist a beer with that arm.

Ford specs full synthetic 75w-140 for this diff, unsure why. I know that during the first few years of F-150 production they spec’d 75w-90 and wrote a TSB bumping the visc to 75w-140 and carried that forward to all production years since.

It was an extensive surgery. 90% torn from the bone supraspinatus, collapsed and arthritic AC joint, over 1” of bone spur pushing down on my supraspinatus. All good now though. I’m in pretty good shape and muscular, which the doc told me would greatly speed my recovery. I’m still doing my best not to use my left arm, but I have almost complete range of motion back at this point…which could end up being detrimental as it makes me a little too froggy and wanting to get back to living normal again

 

[Passport1]

Wow, you'd better wait 'til spring training to show off your curveball.

 

[Panda87]

Wow, you'd better wait 'til spring training to show off your curveball.

Well played sir

 

[SubieRubyRoo]

For curiosity’s sake, why don’t you consider mixing brands a good idea?

I think in gear oils there’s much less opportunity for additive clash like there is with engine oils, but I may be wrong there. But each gear oil has its specific approach to gear protection, and the additives and base oils, if mixed in significant portions, may not protect as expected. In my 75w90 testing thread, several oils had standout performances. Mixing them could possibly negate the strengths of a given gear oil, and combine the negatives of both fluids.

If switching brands, I’d either just do a full drain and fill, or drain and fill with Diff Life Cleaner for a short time and then go to the new fluid. There’s no benefit to mixing gear oils. I do find it curious they require 75w140 for your year. My 2019 calls for 75w90 and has a much higher tow rating. Good luck!

 

[burbguy82]

I agree with @SubieRubyRoo mixing stuff is not a good idea for the long term. But this is a heated debate here. Ready for the battle @SubieRubyRoo ? HAHA.

Contrary I see no issue in heavier gear oil, but I think it depends on usage. On my 1986 M1008, it specs 80w90, i sed 75w140 Synthetic, since it has 4.56 gears. I figure the amount of work the oil is doing is greater as the pinion is spinning faster, more shear. I might be wrong.

Amsoil has a 75w110 oil, best of both world maybe? not sure if HPL has this option. I have though of using the diff cleaner just to try it out.

 

[SubieRubyRoo]

I agree with @SubieRubyRoo mixing stuff is not a good idea for the long term. But this is a heated debate here. Ready for the battle @SubieRubyRoo ? HAHA.

Contrary I see no issue in heavier gear oil, but I think it depends on usage. On my 1986 M1008, it specs 80w90, i sed 75w140 Synthetic, since it has 4.56 gears. I figure the amount of work the oil is doing is greater as the pinion is spinning faster, more shear. I might be wrong.

Amsoil has a 75w110 oil, best of both world maybe? not sure if HPL has this option. I have though of using the diff cleaner just to try it out.

HPL has 75w110. I ordered it before I talked with Dave and he told me the 75w90 was more than robust enough for my 500+rwhp. Oh well…

 

[Panda87]

I think in gear oils there’s much less opportunity for additive clash like there is with engine oils, but I may be wrong there. But each gear oil has its specific approach to gear protection, and the additives and base oils, if mixed in significant portions, may not protect as expected. In my 75w90 testing thread, several oils had standout performances. Mixing them could possibly negate the strengths of a given gear oil, and combine the negatives of both fluids.

If switching brands, I’d either just do a full drain and fill, or drain and fill with Diff Life Cleaner for a short time and then go to the new fluid. There’s no benefit to mixing gear oils. I do find it curious they require 75w140 for your year. My 2019 calls for 75w90 and has a much higher tow rating. Good luck!

So this may be a miscommunication on my part. That “frankenbrew” of gear oils is all Amsoil with the exception of 1/2qt of HPL’s Diff Cleaner. I just used up the last of my remnant bits of SG as a carrier for the HPL Diff Cleaner. I’m certainly not planning to use this blend with the cleaner in it long term, just a cleaning cycle of the diff.

 

[Panda87]

HPL has 75w110. I ordered it before I talked with Dave and he told me the 75w90 was more than robust enough for my 500+rwhp. Oh well…

Well I should have spoken to Dave then, lol. He and I have chatted about the results in the primary chain case in my Road Glide. I’m wondering if the Ford spec for mine using the 75w-140 is due to the loads placed on the gears when towing? I’m pulling 7000-8000lbs behind my Navigator with my family of 6 in it. 500+RWHP is a tremendous load on gears as well, so perhaps the hot 90wt would do fine in a towing application?

 

[SubieRubyRoo]

Well I should have spoken to Dave then, lol. He and I have chatted about the results in the primary chain case in my Road Glide. I’m wondering if the Ford spec for mine using the 75w-140 is due to the loads placed on the gears when towing? I’m pulling 7000-8000lbs behind my Navigator with my family of 6 in it. 500+RWHP is a tremendous load on gears as well, so perhaps the hot 90wt would do fine in a towing application?

I pulled a 9500lb 26’ enclosed trailer into the WV & NC mountains and had no issues, and managed to get 14.8mpg. I thought it was a decent showing.

There’s always the next fluid change…

 

[Panda87]

I pulled a 9500lb 26’ enclosed trailer into the WV & NC mountains and had no issues, and managed to get 14.8mpg. I thought it was a decent showing.

There’s always the next fluid change…

Brother I barely get that sort of MPG completely unloaded with this old beast . It averages about 12.5 unloaded and about 7.5 when towing the camper.

 

[vwmaniaman]

I had my right shoulder dislocated when I had hernia surgery because I coded on the operating table. They jerked me off that table to resuscitate me but I was in a coma for 3 days. When I went home I couldn't even pickup my coffee cup. I talked to a preacher that prayed for me and told me about 50mg DHEA tablets. After taking them for a month I was able to use my right arm again. I have a 65 VW bug and I couldn't even pull up the lock button without walking my fingers across the seat back to get to it. I still take DHEA today since it helped me so much in my joints.

 

[Panda87]

I had my right shoulder dislocated when I had hernia surgery because I coded on the operating table. They jerked me off that table to resuscitate me but I was in a coma for 3 days. When I went home I couldn't even pickup my coffee cup. I talked to a preacher that prayed for me and told me about 50mg DHEA tablets. After taking them for a month I was able to use my right arm again. I have a 65 VW bug and I couldn't even pull up the lock button without walking my fingers across the seat back to get to it. I still take DHEA today since it helped me so much in my joints.

I’m glad you survived all that! Shoulder surgery is nothing to sneeze at, that’s for dang sure. During the first week, I couldn’t put deodorant on my right armpit and had to rest my left hand on the counter and lean away to get enough space to coat my left one. It looked goofy, but worked, kind of like having to walk your fingers to reach the lock. What caused you to code during the surgery?

Since reading what you posted, I’m wondering if part of the reason I heal so quickly may be due to the sky high levels of DHEA-S and IGF-1 I produce endogenously. I know IGF-1 levels correlate to bone growth speed. DHEA-S affects soft tissue growth and masculine traits. Only substances I lacked were SHBG and Testosterone. SHBG is still floored, but I’m on TRT now to fix the test. As far as supplements that I believe are helping me, I’m taking a multi twice a day, 3g fish oil, magnesium glycinate, glucosamine/chondroitin/MSM, Vitamin D, Vitamin C, 48oz milk for calcium, 200g protein minimum, etc.

Attached is one of my labs:
DHEA-S Level: 418 ug/dL. Reference range stops at 416.
IGF-1: 268 ng/mL. Reference range max is 290.

 

[Rob_Roy]

Does your Navi have a LSD? Our 2016 Expedition did, and it seemed to darken the fluid fairly quickly. I also had to add a bottle of Ford FM to get it to stop chattering on turns, despite using a fluid made for LSD.

 

[Panda87]

Does your Navi have a LSD? Our 2016 Expedition did, and it seemed to darken the fluid fairly quickly. I also had to add a bottle of Ford FM to get it to stop chattering on turns, despite using a fluid made for LSD.

I wish! This one is open diff with the electronic lockers. Only vehicle that ever had an LSD was my 04 Ram. I miss having an LSD for sure, lol.

 

[fantastic]

First, keep using the 75-140 in your rear diff as the manual states. When one says "Mine uses 90" that most likely was after Ford beefed up the axles when they were wanting to reduce weight on that 1/2 ton. That is not equal, same thing can be said about "my old F150 truck uses 10w-30 engine oil" while the next person claims "my newer F150 uses 5w-20 so you should be fine". Again, you already know this... KEEP USING 140! LOL Especially, as more wear is present over time/mileage. Ford used 140 for many years on their lighter duty axles. My Dana 80 uses 80-90 (heavier duty built so 140 not necessary) but I use 75-140 now anyways. you did fine on mixing the scraps for a short duration of cleaning cycle. I do see the gray color in that rear fluid & I'm not certain other than metal wear being cleaned up like you mentioned but at your mileage there is more wear happening as well (snowball effect). Every rear diff I've opened I feel like fainting from the Propane aroma it pummels at you. You can buy "Lube Locker" brand gaskets that are reusable & no gasket maker use is necessary when using one. The only real way you get moisture inside the axle is if you're driving through water up to your axles basically.

 

[thastinger]

Ford specs full synthetic 75w-140 for this diff, unsure why. I know that during the first few years of F-150 production they spec’d 75w-90 and wrote a TSB bumping the visc to 75w-140 and carried that forward to all production years since.

It was an extensive surgery. 90% torn from the bone supraspinatus, collapsed and arthritic AC joint, over 1” of bone spur pushing down on my supraspinatus. All good now though. I’m in pretty good shape and muscular, which the doc told me would greatly speed my recovery. I’m still doing my best not to use my left arm, but I have almost complete range of motion back at this point…which could end up being detrimental as it makes me a little too froggy and wanting to get back to living normal again

My 98 F150 Sterling 9.75 calls for 75-140, it is right on the metal tag attached by the diff cover bolts. I'm not aware that Sterling ever called for 75/80-90.