Does rear diff have a reusable gasket?

[jjack50]

I tried to find what Ford spec'd for the Bronco but didn't find it, since I know Ford uses synthetic gear oil in other applications. I threw that out there as another perspective, since so many things around topics like this are speculative with little real hard studies or info. Currie requires conventional oil with a GL-6 rating for higher pressure resistance, and they say that current synthetics are GL-5 rated, which in their opinion is less desirable in the 9" style rear ends that they build, yet they say the same thing for the Dana 60/70 based RockJock rear ends that they build. My point was simply not to assume that a synthetic gear oil is better or superior to conventional gear oils.

Regarding Ford using synthetic gear oil I know they spec synthetic oil in Super Duty pick ups, and we rebuild quite a few (relatively, not very many in pure numbers) failed rear ends in Super Duty trucks. What I see happening, and this applies to quite a few situations, is the factory uses synthetic to extend service intervals as a selling feature. In the real world when vehicles get over 100k miles fluids should be changed due to wear no matter what, but because of the synthetic it doesn't get serviced, and can eventually cause a failure. To add some context here, I worked at dealerships for 29 years, and now have owned my own independent auto repair shop for 11 years, so I've seen it all.

Factories more and more are putting out "lifetime" fluids and parts. Modern vehicles are too well built, and cost too much to replace, and can and will be driven for multiple hundreds of thousands of miles and nothing on the vehicle is truly lifetime. One example is u-joints which on all vehicles now are non-serviceable. We insist on replacing u-joints on any rear wheel drive vehicle over 150k to prevent drivelines from falling out on the road, which has happened many times. We recommend replacing engine oil and rear end gear oil because the oil collects contamination even if the synthetic oil maintains it's properties longer than conventional oil. To me, if the synthetic lubricates better, then don't loose that benefit by negating that effect by running it longer with some contaminants in the oil. If there is to be a benefit, change it more often, otherwise the only benefit is not needing to service it as often. And, you can pay twice as much for a synthetic service, so do two conventional services or one synthetic service. I'd rather have two conventional services and have cleaner oil for half the time. Point is to service synthetic oils more frequently than the factory recommends, to actually get a benefit from using the synthetic oil.

I know this is long, forgive me is this is boring, but here is another example. I have a friend with a Ford Powerstroke truck, and he swears by Amsoil oil. He doesn't change it very often, like 80-100k miles, but he regularly takes a sample and sends it off for analysis, and he changes the oil when the analysis says it's time. He has replaced his turbo 3 times, at 150k intervals. I drive Powerstrokes, and know tons of people who drive Powerstrokes, and read forums, etc. No one else that I see has to replace a turbo every 150k miles, and virtually everyone with a Powerstroke uses Delo or Rotella conventional oil. He is so sold on Amsoil that he won't consider that the much longer service intervals are his problem. He says "well I get it analyzed". Pretty simple to see.

From the 2022 Bronco manual Ford diff oil spec is Motorcraft® SAE 75W-85 Premium Synthetic Hypoid Gear Lubricant(U.S.).

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[flip]

Just a heads up, your system shows both those items as not compatible when I looked them up on your parts website

The parts store (Revolution Parts) pull the info from Motors which is months behind on updates. I've added parts along with pics and descriptions manually for a bunch of items because of this. I did look this up for '21-'22 Bronco in Microcat so just ignore the store, it's just way behind. They told me the complete update takes about a year so near the end of '22, '21 should be mostly loaded. Yea, great

 

[FlyingScot]

The parts store (Revolution Parts) pull the info from Motors which is months behind on updates. I've added parts along with pics and descriptions manually for a bunch of items because of this. I did look this up for '21-'22 Bronco in Microcat so just ignore the store, it's just way behind. They told me the complete update takes about a year so near the end of '22, '21 should be mostly loaded. Yea, great

Ha, figured that was the case. Makes me feel better about the dumpster fire cleverly disguised as logistics software we had at my last job.

 

[SubmarineNuke]

So as I just got my MetalCloak rear diff cover this thread is useful…sorta.

Per @flip it looks like the gasket is reusable and should be fine.

But no general consensus on gear oil to refill the diff? I don’t want to F this up as this is new territory for me. Should I buy a new gasket from auto zone or where ever? Should I use royal purple? What is the best suggestion here.

 

[flip]

KB3Z-4036-A reusable gasket
Motorcraft® SAE 75W-85 Premium Synthetic Hypoid Gear Lubricant / XY-75W85-QL Fill to bottom of plug about 4 pints

Torque:
Stage 1: 177 lb.in (20 Nm)
Stage 2: 25°

 

[FlyingScot]

So as I just got my MetalCloak rear diff cover this thread is useful…sorta.

Per @flip it looks like the gasket is reusable and should be fine.

But no general consensus on gear oil to refill the diff? I don’t want to F this up as this is new territory for me. Should I buy a new gasket from auto zone or where ever? Should I use royal purple? What is the best suggestion here.

Redline's 75W85 GL-5 gear oil is good for the rear diff if you're not a fan of the Motorcraft offering

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