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

[Pablo]

I would NOT change viscosity. And if you did, why 90? Why two steps, lower viscosity? Maybe, maybe think 110.

Anyway, the fluid definitely looks contaminated. Hazarding a guess it had some intrusion (water, dirt, wrong juice) at some point in the past and the simple drain didn't get it out. New fluid just picked it up.

Mixture doesn't bug me as a short, very short flush run. Might actually help as a flush.

Get better SOON. Just thinking about that feels painful!!

 

[Panda87]

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.

I had happened across that info a while back and didn’t bother to save it because it didn’t apply to my application. Since I tow, I’ll stick to the 75w-140 though. I wish I had a cool metal tag on my diff saying that. Heck, maybe I do but there’s that **** cross member right behind the cover, lol

 

[Panda87]

I would NOT change viscosity. And if you did, why 90? Why two steps, lower viscosity? Maybe, maybe think 110.

Anyway, the fluid definitely looks contaminated. Hazarding a guess it had some intrusion (water, dirt, wrong juice) at some point in the past and the simple drain didn't get it out. New fluid just picked it up.

Mixture doesn't bug me as a short, very short flush run. Might actually help as a flush.

Get better SOON. Just thinking about that feels painful!!

Thanks Pablo! I agree with you, I think the SG definitely cleaned some gunk in there and ended up mixing it in. I still have that jar of old gear oil sitting on my desk and waiting to see if it will stratify any water to the top. Nothing yet, lol.

I appreciate it man! I’m doing pretty well all things considered. Replacing rear CV axles and all of the control arms in the rear of the Navigator this past weekend has me pretty dang sore . I was feeling a little too good apparently, haha

 

[Chris142]

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.

ya ford recommended 140 way back. My 87 f250 says to use 140.

 

[wpod]

I use 75W-140 in everything. More cushion for the pushin.

 

[Panda87]

I use 75W-140 in everything. More cushion for the pushin.

I like my lubes like I like my women, thick and cushiony

 

[Impatient]

My 2019 calls for 75w90 and has a much higher tow rating. Good luck!

I have a 2015 Ford Transit 250 hi-top (tallest) with 9.75 rear. Factory fill is 75w85. I have no doubt older Fords had 75w140, but I’m surprised by Subie’s claim 2019 specs 75w90. I was going to get SG 75w90, but Pablo posted a 75w110 suggestion…which I didn’t see for awhile since I’m laid up myself with 2nd bone fracture event in 5 months, and some other big family issues.

But my question/curiosity is: did Ford really drop from (75w)140 to 85, then back up to 90?

I don’t tow, seem to have a mere 7500lb total camper-build weight, and It does have the ridiculously hi 3.31 ratio and the turbo EB. Rear tires are larger than stock, but still ridiculously small at 225/75r16, was denied going to an even larger rear tire by Discount Tire. I was stressing going “up to” 75w90, let alone 75w110.

Again, did Ford walk back their fuel-economy-focussed 75w85 recommendation?

 

[SubieRubyRoo]

I have a 2015 Ford Transit 250 hi-top (tallest) with 9.75 rear. Factory fill is 75w85. I have no doubt older Fords had 75w140, but I’m surprised by Subie’s claim 2019 specs 75w90. I was going to get SG 75w90, but Pablo posted a 75w110 suggestion…which I didn’t see for awhile since I’m laid up myself with 2nd bone fracture event in 5 months, and some other big family issues.

But my question/curiosity is: did Ford really drop from (75w)140 to 85, then back up to 90?

I don’t tow, seem to have a mere 7500lb total camper-build weight, and It does have the ridiculously hi 3.31 ratio and the turbo EB. Rear tires are larger than stock, but still ridiculously small at 225/75r16, was denied going to an even larger rear tire by Discount Tire. I was stressing going “up to” 75w90, let alone 75w110.

Again, did Ford walk back their fuel-economy-focussed 75w85 recommendation?

My bad… the pic below shows it’s 75w85 according to Ford, I think I got the 75w90 by referencing Amsoil website. Either way, a 75w85 is soooo similar to a 75w90 they’re essentially identical. Considering Ford specs a blend, a full syn 75w90 will outperform the required fluid every time. You can search my rearend thread, even though I waited til like 77k to change the rear diff fluid, the gearset looked immaculate. Now that it’s got HPL 75w90, I expect no further degradation regardless of how long I keep the truck.

 

[Impatient]

Well, @SubieRubyRoo, reading your attachment, looks like the Ford 75w-85 is “Premium Synthetic,” no mention of the word “blend.” This is one reason I’ve been reluctant to use a heavier gear oil; I mean, maybe the Ford fluid is truly special. Though, I guess there are other 75w-85’s out there…some better than others??? Are ANY of those blends?

Now, I believe the Motorcraft ATF is conventional, or at least I haven’t seen any credible claim it’s synthetic ( not that I’ve read up on it extensively).

And of course, their engine oil comes in both flavors: full synthetic and blend, with the blend being way more available.

back to gear oils, I’m all for a very low Brookfield, like what you might see in a quality 75w-85, but more high-temp protection than what any of those provide…assuming viscosity is needed for hi-temp gear shock protection.

 

[proffittmarke]

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.

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I use Amsoil engine oil, but am not impressed with their differential fluid. Had similar issue. I like Motul differential fluid. Cheap at Summit.

 

[wlk]

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.

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You are fine running your leftovers for a short run. Ford back spec'd the 75w140 after complaints of whining coming from the rears w 75w90. My 05 Expedition was one of the years affected by this. Keep us posted on how the cleaning phase goes. Thanks for posting.

 

[Impatient]

I use Amsoil engine oil, but am not impressed with their differential fluid. Had similar issue. I like Motul differential fluid. Cheap at Summit.

Hmmm, Amsoil Severe Gear came out at / near top of the heap in the testing @SubieRubyRoo commissioned. What’s your concern with it, other than price…which isn’t that bad compared to OEM fluids.

 

[SubieRubyRoo]

Hmmm, Amsoil Severe Gear came out at / near top of the heap in the testing @SubieRubyRoo commissioned. What’s your concern with it, other than price…which isn’t that bad compared to OEM fluids.

Amsoil Severe Gear is absolutely a premium fluid. Even David said it’s a very good option. It’s proven its mettle, and call @Pablo if you want some.

 

[proffittmarke]

Hmmm, Amsoil Severe Gear came out at / near top of the heap in the testing @SubieRubyRoo commissioned. What’s your concern with it, other than price…which isn’t that bad compared to OEM fluids.

Amsoil is good in limited slip applications. Is not ideal for locking differentials. I worked in an automotive testing facility and am not fond of one-size-fits-all lubricants. GM has two different rear diffs on 4X4 and they require different 75W85 fluids. Never had any issues since I switched to Amsoil in 1994, until now.

 

[Pablo]

Amsoil is good in limited slip applications. Is not ideal for locking differentials. I worked in an automotive testing facility and am not fond of one-size-fits-all lubricants. GM has two different rear diffs on 4X4 and they require different 75W85 fluids. Never had any issues since I switched to Amsoil in 1994, until now.

Does it depend on type of locking differential? It works fine in Toyota elockers and all air lockers

 

[Panda87]

Update for everyone! My little science experiment of letting the mason jar of gear oil sit in my office has borne fruit! It would appear the Amsoil SG had cleaned the differential and held the particulates in suspension. After a great length of time, those particulates have settled to the bottom of the jar as a very dark gray slurry while the gear oil itself has changed to a dark honey color as the particulates settled to the bottom.

Looks like the Amsoil SG did exactly what it was supposed to! @Pablo this one points to the SG base oils as fantastic for cleaning up a diff/gear sets.

 

[CheezWhiz]

everyone knows that gear oil lasts forever!

 

[tcp71]

My 2009 F150 with 9.75 axle spec'd 75w140. My 2016 F150 with 9.75 axle spec's 75w90. I changed the fluid on the 2016 at 20k miles (and a second time shortly after because the felpro gasket I tried to use leaked) with Ford 75w140 left over from my 2009 truck. It's been in there since 2018. Last summer I opened the fill plug to see it's condition and the few drops that came out looked like new fluid. I didn't change it, nor do I expect to in the near future. This truck tows 7500lbs 2-3000miles every summer through the rockies. Your fluid looks a bit grey-ish, but nowhere near one that has water in it.

 

[Panda87]

My 2009 F150 with 9.75 axle spec'd 75w140. My 2016 F150 with 9.75 axle spec's 75w90. I changed the fluid on the 2016 at 20k miles (and a second time shortly after because the felpro gasket I tried to use leaked) with Ford 75w140 left over from my 2009 truck. It's been in there since 2018. Last summer I opened the fill plug to see its condition and the few drops that came out looked like new fluid. I didn't change it, nor do I expect to in the near future. This truck tows 7500lbs 2-3000miles every summer through the rockies. Your fluid looks a bit grey-ish, but nowhere near one that has water in it.

My navigator tows the same amount of weight as you do. This was what I assume to be the first drain and fill of this diff in 150k miles. Needless to say, the Amsoil had its job cut out for it dealing with all the particulate matter that didn’t drain and any varnish left behind by the factory fill. The updated pic shows that what the SG looked like after draining was mostly particulate matter that ended up settling out of suspension.

 

[dnewton3]

If there is anything I've learned from my trips to HPL, including the open-house event two years ago and a individual tour, it's that you should NOT mix brands/grades of boutique lubricants.

It is generally very safe to mix most store-bought API licensed fluids for any particular application, mainly because most API licensed fluids don't really stretch the envelope when it comes to additives, etc. It's not like a little more or less of Ca or Mg, etc, is going to upset the apple cart ...

But boutique lubes like Amsoil, RP, RL, and especially HPL are tailored to specific goals and often have very unique chemistry. For example, the anti-foam package in HPL lubes is sensitive to the % ratio of concentration. Further, the lubes may or may not have additives which compete for solubility, etc. Then there's the esters, ANs, etc ... Even ZDDP can be an issue if too much is present. This is like the whole "Goldilocks" topic; too much or too little of a good thing is a bad thing. When you mix products without knowing the EXACT additive package in both, and how they will interact with each other, you have no idea of what effects you may be creating.

Amsoil makes great products. HPL makes great products. But without knowing the potential for chemical coercions pro and con, I'd advise to stay away from mixing them.
- mixing them MIGHT be of benefit
- mixing them MIGHT be a wash
- mixing them MIGHT be detrimental
And you have no way of knowing, because unless you're privy to the formulators notes and such, you're never going to fully know what's inside the bottle. An ICP analysis is only going to tell you so much, and it will never tell you about the many additives it simply cannot see; many of which are very sensitive to interactions and concentrations relative to their full performance potential.

What you can do, and what you should do, are two different things.