Whirring or grinding sound on 2022 through 2025 Lincoln Navigator (front differential)

[NavigatorPro]

This thread is in regards to the Ford Expedition, Ford F150, Ford F150 Raptor and Lincoln Navigator front differential problems in the 2021 through 2025 model year vehicles. Im posting this here because I want to be helpful to whoever finds it. There are a bunch of different threads on Reddit and in F150 forums about it.

My former vehicle was a 2023 Lincoln Navigator L and it developed a whirring noise on the front left which turned into a grinding noise. Every time I took it to the Ford dealership I kept getting the run around. One day I took it to an independent mechanic who was extremely helpful and way better than the technicians at the Ford dealership. He showed me the front differential. Fluid was black (out of a new bottle its clear) and there was a glittery silver metal running through it. He told me the front differential was literally eating itself. I took photos and went back to the Ford dealership. The next thing I knew they had my truck for over a month. When I got the truck back there was that noise again. Took the truck back to the dealership and they replaced the left wheel bearing...still there was that noise...took it back and they replaced the the right wheel bearing...still there was that noise. This eventually ended one day when I sold the vehicle to Carvana and got myself a 2025.

I thought all the problems of the 2023 "Covid trucks" were solved in 2025...little did I know that I was wrong. All of a sudden I heard that whirring noise. This time I took it to an independent mechanic to have a look. He told me the front differential was leaking and showed me the entire bottom was wet with gear oil. Furthermore he ended up adding gear oil stating there was only 1 quart of gear oil left in it. After that I drove it around and looked underneath. Sure enough there was a drip. I took it to the Ford dealership and after 1 hour their best technician took me aside, looked me in the eye and told me it was the fill plug...he told me there was not enough sealant on it. The gear oil was passing through the threads.

So I left the Ford dealership and take note I will never go to that one again. Either they were deliberately lying to me or they did not know what they were doing. I went right back to the independent mechanic and decided to take matters into my own hands. I spoke with the independent mechanic and asked if he knew where it was leaking and what he needed to do to fix it. Affirmative! He told me what he needed and that was "Permatex Grey". I enjoy being informed about these matters so I turned to the internet for a crash course on sealant. There is Permatex Ultra Grey and Permatex Optimum Grey. The Optimum Grey is an improved version of the Ultra Grey. I went around to 3 parts stores and finally found a single tube on the shelf of the Optimum Grey. Apparently Optimum Grey is a very popular product around here.

The "fix" the mechanic told me was to take off the metal cover on the differential...there are several bolts...and seal it with the Permatex. He pointed out there is no gasket between the cover and the differential. I looked on the Ford parts website and he was right. Somehow Ford thought it was a good idea to have no seal between the cover and the differential. (see attached image).

Yesterday the entire truck was left at the mechanic at 8am. On the Reddit and Permatex website there were certain ways to use these sealants to perfection. After use you really should not disturb it for at least 6 hours, but preferably 24 to 48 hours. After the work was done I opted to pickup the truck 15 minutes before the mechanic closed for the day allowing it to sit for at least 6 hours. I drove the truck right back to home which wasnt far and its been sitting in my driveway. Im going to try to leave it alone in the driveway until it reaches at least 24 hours from the time of installation. In various forums it was suggested to leave it sit overnight. One forum even stated to try not to disturb it for 48 hours.

As for the gear oil to use, prior to 2015 was 80w90 in the front and 75w140 in the rear. After 2015 because of government CAFE mpg (fuel economy) requirements its been 75w85 in both front and rear. I went with Amsoil 75w140 in both front and rear differentials. Amsoil is well known for putting out premium oil products and since these differentials only hold 2-3 quarts I figured it was a good idea to get the best. There wasnt much of a price difference between the Valvoline gear oil on the Walmart shelf and the mail-order Amsoil. To sum up you absolutely should not put the 75w85 into the differential. If you really want it to last you should go thick and get a premium gear oil. Ive read about different change intervals on the internet. Conventional internet wisdom states to change it at least every 50,000 miles, but some state 30,000 miles. There is a tendency for water or condensation to get into these things and for offroad or oil field work thats something to think about. Take note some people advised me to go a little thinner on the front differential and that advice was noted, but I decided to go the thicker route. The differential was leaking...had problems with the front differential in the past...lets go thick and dont look back.

To sum up if you are hearing a whirring noise up front and to the left on a Ford or Lincoln truck / suv than carefully examine the front differential for leaks. Its not hard to crawl underneath the front and take a look yourself. Start at that point.

 

[Mark-P]

Thanks

 

[G-753075]

Do you have a single-speed transfer case
-@akras

 

[Hanyol0]

Wasnt tracking this as i have a 23 Nav L and going to check tomorrow for a leak. I dont hear a noise yet.

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[NavigatorPro]

Wasnt tracking this as i have a 23 Nav L and going to check tomorrow for a leak. I dont hear a noise yet.

The Navigator off of the new car lot is quiet. Any noises you hear are basically warnings about an impending problem and are not natural to the vehicle. Thus a whirring noise coming in from the left front is most usually associated with the front differential and means the gear oil level is too low. If you crawl underneath the front of the Navigator there is a heavy cloth like splashshield bolted in protecting parts like the front differential. You can pull it back and observe. I attached a photo and thats what it looks like. The large black bolted in cover faces the front and thats what you can see if you pull the undershield back. You can also take a ratchet to unbolt the undershield.

If any part of the large black metal bolted in cover looks wet its probably gear oil. It should look and feel dry to the touch. The solution to the leak is to unbolt and remove the large black cover and seal the leaking portion with Permatex Optimum Grey or Ultra Grey. This is basically a gasket maker and this front differential lacks a gasket and this Permatex product will harden into a gasket-like form. The Optimum Grey is the new improved product over the Ultra Grey.

Another note about the leak is it will usually be drip drip and right after driving the vehicle look underneath the front for that drip of gear oil.

To be clear the whirring sound means the front differential is low on fluid and needs to be corrected immediately. If you go to the dealership you will get the run around and so I suggest to save time and a possible part failure go to the independent mechanic. A tube of Permatex Optimum Grey can be found at the local Advanced Auto or Autozone. If you were to unbolt the black cover on the differential there is no gasket behind the cover thus why its leaking.

Another part to get at the parts store is 75w140. I suggest Amsoil 75w140 but what they usually have at the local Walmart and parts store is Valvoline 75w140. It will take 2-3 days to get the Amsoil by ordering it online. The Valvoline isnt as good as Amsoil but better than what the truck came stock with. The truck came stock with 75w85 which is a thin gear oil strictly used for fuel economy purposes. The doubly thick 75w140 will make the front differential last longer and stronger...less future issues. On both the front and rear differential I suggest a change interval of 30000 to 50000 miles.

Keep in mind on the F150, Expedition and Navigator the front axles spin even in 2 wheel drive mode meaning the front differential is also spinning as well and so the oil is getting used. Since the Navigator is based off the F150 truck dont be afraid to take it to an independent mechanic. Finding a good independent mechanic is an entirely another thread. I can warn you there are a lot of quack mechanics out there...

 

[akras]

Unfortunately, these differentials can be problematic even when they don't leak and the oil level is normal. My understanding is that the pinion bearings don't get enough lubrication because of what can be considered a design flaw. Thicker oil is a good idea: I will be replacing the factory oil with 75W-140 in my new front differential. Amsoil Severe Gear is among the best, if not the best gear oil. Another questionable engineering decision that doesn't help is the engagement of the front differential in the 2WD modes. I heard that Navigators with a 2-speed transfer case don't do it, but I wasn't able to verify this info.

A few more things.

1. There is no good reason to remove the cover just to change oil (if there are no leaks): drive a bit to suspend any metal particles in oil and suck the oil out through the fill plug using a small hand pump.
2. To seal the plug, one should use a specialized thread sealer. I use Permatex 59214 High Temperature Thread Sealant. Using a gasket sealant, while works and used by some mechanics, is suboptimal.
3. Changing gear oil /other fluids more often than recommended is a very good idea (just like with the motor oil). I did it recently (at about 65 kmiles), and the worst oil was in the front differential (perhaps because a bearing was eating itself; no metal shavings though); the rear was better, but still very different from new. Transmission fluid also looked overdue for replacement. Interestingly, the transfer case fluid looked brand new: I replaced it, but I probably won't touch it again.
4. I probably wouldn't put 75W-140 in the rear differential. A thicker oil is a good idea, but if you drive in winter temperatures, 75W-140 is too thick and is likely to have noticeable effect on fuel economy. Note that, while front differential always spins, the transfer case sends a very low fraction of the torque to it unless required, so I wouldn't expect a noticeable difference in mpg in 2WD modes with a thicker oil in the front. The rear is different, especially in winter. Next gear oil change I will be putting something in between the stock viscosity and 75W-140 in the rear differential (but 75W-140 in the front). In any case, I haven't heard that rear differentials have bearing lubrication problem, unlike the front ones.
5. While F-150 (and some Expeditions) use essentially the same front differential, the gear ratio can (and likely will) be different, so one has to verify it before ordering. But from the point of view of a mechanic who replaces it, no difference whatsoever. If they can do a F-150, they can do a Navigator, that's true.

 

[NavigatorPro]

Unfortunately, these differentials can be problematic even when they don't leak and the oil level is normal. My understanding is that the pinion bearings don't get enough lubrication because of what can be considered a design flaw. Thicker oil is a good idea: I will be replacing the factory oil with 75W-140 in my new front differential. Amsoil Severe Gear is among the best, if not the best gear oil. Another questionable engineering decision that doesn't help is the engagement of the front differential in the 2WD modes. I heard that Navigators with a 2-speed transfer case don't do it, but I wasn't able to verify this info.

A few more things.

1. There is no good reason to remove the cover just to change oil (if there are no leaks): drive a bit to suspend any metal particles in oil and suck the oil out through the fill plug using a small hand pump.
2. To seal the plug, one should use a specialized thread sealer. I use Permatex 59214 High Temperature Thread Sealant. Using a gasket sealant, while works and used by some mechanics, is suboptimal.
3. Changing gear oil /other fluids more often than recommended is a very good idea (just like with the motor oil). I did it recently (at about 65 kmiles), and the worst oil was in the front differential (perhaps because a bearing was eating itself; no metal shavings though); the rear was better, but still very different from new. Transmission fluid also looked overdue for replacement. Interestingly, the transfer case fluid looked brand new: I replaced it, but I probably won't touch it again.
4. I probably wouldn't put 75W-140 in the rear differential. A thicker oil is a good idea, but if you drive in winter temperatures, 75W-140 is too thick and is likely to have noticeable effect on fuel economy. Note that, while front differential always spins, the transfer case sends a very low fraction of the torque to it unless required, so I wouldn't expect a noticeable difference in mpg in 2WD modes with a thicker oil in the front. The rear is different, especially in winter. Next gear oil change I will be putting something in between the stock viscosity and 75W-140 in the rear differential (but 75W-140 in the front). In any case, I haven't heard that rear differentials have bearing lubrication problem, unlike the front ones.
5. While F-150 (and some Expeditions) use essentially the same front differential, the gear ratio can (and likely will) be different, so one has to verify it before ordering. But from the point of view of a mechanic who replaces it, no difference whatsoever. If they can do a F-150, they can do a Navigator, that's true.

If you take the cover off the differential you can get in there with a dry rag and wipe out all the metal particles. Sometimes there is a bit of a metal mess waiting in there. This is how it is as well when the pan is taken down from the transmission. Usually there is a little metal mess waiting in the bottom of the pan. I also noted when the magnetic fill plug was taken out there was black metal sludge on it that needed to be cleaned.

 

[NavigatorPro]

I read in this forum that someone had worked with an independent mechanic and got the entire differential replaced for $1200. Believe me if I knew that was an option back in year 2023 I would have done it myself outside of the warranty! The warranty and repair process took over 30 days and when I got the vehicle back I was still hearing some differential noise. I emailed that person and they told me the part was S993K. I looked it up on Google and not sure what that comes with exactly.

I use my truck for work purposes and if someone told me back in 2023 they could remedy the situation for $1200 I would have thrown down that money right away!!! It was a nightmare getting it replaced under warranty!

Again, I have no idea what is included with part S993K or what needs to be done, however, if this happens again I will be going to my local mechanic and seeing if this is an option...

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[akras]

S993K is a complete assembly, including gear oil. Installation is very straightforward. In addition, it makes sense to replace older IWEs with a new version when the axles are pulled from the hub (for vacuum-operated IWEs; newer Navigators have a different design there, which appears to be less problematic).

 

[NavigatorPro]

Here is some other notes I wanted to include in this thread...

- In 2023 there was a national shortage of front differentials so when my differential went out the dealership decided to rebuild it. It took them 30 days to rebuild it and I felt that my Navigator still had that noise. I believe it was the dealerships fault in taking so long and this dealership I heard has a history of bad service. Today, my understanding is there are front differentials ready to ship. So if I had to do it all over again and the differential went down today I would first ask very directly how long it will take and explain if it cant be done in a week than I will go down the replace out of pocket route. The 30 days being out of a car really cost me and I would have paid out of pocket for a new one if I knew it would have been out so long.

- Prior to 2015 Ford had used 75w-140 in the rear differential and 80w-90 in the front differential. The switch to 75w-85 was purely for fuel economy, but not long term reliability or severe service. Fords "Super Duty" trucks still use the old combination of 80w-90 in the front and 75w-140 in the rear. 75w-85 is the thinnest gear oil out there and its a better idea to go thicker. If you think 75w-140 is too thick there are other thinner gear oils out there like 80w-90, 75w-90 (a popular option), and 75w-110.

Here is a link to Amsoil's data sheet and you can see the thickness of the oil.

https://www.amsoilcontent.com/ams/lit/g2043.pdf

Since I have had problems with front differentials in the past to include leaking recently and in 2023 it was the gears itself I have opted to go 75w-140 front and back. Many people opt to go with 75w-90. I think if you do off-road, oil field work, work in very hot climates, etc I think you should opt for 75w-140 without a doubt...front and back. Its up to you.

 

[Action]

Gear oil weight is not the only measurement of a lubricant.
That weight is just a measurement of flow.
Additive packages to all lubricants can make different oils better at lubricating.

Otherwise, automatic transmissions would be using Type F today.
Or using 10w40 oil in an engine would be a good thing.

The switch to a thinner lubricant for fuel economy is not made lightly. Manufacturing processes change to accommodate the thinner lubricant. And an additive package is added to the mix.
The ability of the lubricant to maintain the viscosity or weight. (and not thin out in service) This includes physical and chemical stability.
The ability to keep metal parts from contact with each other. Film strength
The ability to cling to the metal surfaces when the assembly is not in service. Or adhesiveness.
The ability to prevent corrosion

There are other characteristics as well. Judging the gear oil or any lubricant to a weight becomes a little short sighted.

And as you stated, use of the vehicle is a factor. Off road usage has it's own set of maintenance schedules.

Action

 

[akras]

Yes, it is absolutely important to look beyond just the viscosity. My understanding is that Amsoil Severe Gear oil is among the best (or the best) gear oils out there, exceeds Ford requirements, and is available in a variety of thicknesses, from 75W-90 to 75W-140 and a few in between. Everything else being equal, reasonably thicker oil does provide better film strength and better resistance to thermal runaway.

In my brand new front differential I have swapped the factory oil (it comes with oil already added) for Severe Gear 75W-140; I will be replacing the Ford recommended rear differential oil with Severe Gear 75W-110 when I do the next gear oil change.

As a side note: the oil level in my old differential was normal (and presumably pinion gear bearing(s) failed by 65 kmiles regardless), but the new differential came more than 1/2 quart short on oil. I heard that underfilling differentials at the factory is not uncommon, so it makes sense to check the oil levels on new vehicles.

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