Rear differential fluid change?

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ExplorerTom

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You mean the difference between factory gears installed at the factory vs third party gears installed by a fourth party? I can think of a short list of things. That said, Nitro gear has specific break in instructions for their gears. For seemingly good reasons and that's why I changed the oil. For comparison, there were no gear break-in instructions when I bought the Expedition :).

So you’re saying that the factory installs better gears with a better technique than an aftermarket shop? That’s why a factory sealed diff can go for its lifetime and your aftermarket gears need to be serviced more frequently?

You do realize that’s a bunch of baloney.
 

07navi

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So you’re saying that the factory installs better gears with a better technique than an aftermarket shop? That’s why a factory sealed diff can go for its lifetime and your aftermarket gears need to be serviced more frequently?

You do realize that’s a bunch of baloney.
It's not the gears, it's the oil. Years ago you did have to change it. Like I said somebody thought it was good to change it with the new gears after 500 miles and that's what he did......like it got contaminated or something:emotions34:. It's just very hard steel and oil and the synthetic type makes it work great together. For a loooong time
 

ExplorerTom

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It's not the gears, it's the oil. Years ago you did have to change it. Like I said somebody thought it was good to change it with the new gears after 500 miles and that's what he did......like it got contaminated or something:emotions34:. It's just very hard steel and oil and the synthetic type makes it work great together. For a loooong time

What’s the difference between aftermarket gears with motorcraft gear lube and factory gears with the same motorcraft gear lube?
 

justinp16ex

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Don't think the gears are the big concern in these, I'd be more concerned with the fluid losing it's slipperiness and ability to dissipate heat. Making it unable to protect and affect the proper function of the LSD clutch packs that some of these have. Clutch pack replacement is over $1000 at the dealer. Mine were shot at 100k. Not sure if previous owner serviced the fluid or not. Since it's a 'lifetime' fluid, I'm gonna say it probably wasn't done. These things get hot, I change fluids more often than manufacturer recommends because it is the easiest preventative maintenance you can do.
 

07navi

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Don't think the gears are the big concern in these, I'd be more concerned with the fluid losing it's slipperiness and ability to dissipate heat. Making it unable to protect and affect the proper function of the LSD clutch packs that some of these have. Clutch pack replacement is over $1000 at the dealer. Mine were shot at 100k. Not sure if previous owner serviced the fluid or not. Since it's a 'lifetime' fluid, I'm gonna say it probably wasn't done. These things get hot, I change fluids more often than manufacturer recommends because it is the easiest preventative maintenance you can do.
The LSD diff adds a little to the equation but it's controlled with an additive. The synthetic oil itself doesn't "lose it's slipperiness", that's the glory of it.
 

Vancouver Bob

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So you’re saying that the factory installs better gears with a better technique than an aftermarket shop? That’s why a factory sealed diff can go for its lifetime and your aftermarket gears need to be serviced more frequently?

You do realize that’s a bunch of baloney.

No, that's what you're saying... and like you said, it's a bunch of baloney :).

What I'm saying is ford has control over their design, part quality, and processes. Based on their testing they feel the proper interval for changing differential fluid is 150K miles (unless towing and other severe usage like someone mentioned earlier). The manufacturer of the new gears (as well as other gear manufacturers) recommends a break in of their gears followed by a fluid change after 500 miles. That's what I'm saying.
 

07navi

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I don't understand the 500 mile thing and I never heard of that before. It's not like a rad flush where maybe you didn't get it all the first time.
 

Thunderbirdsport

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I'd change it, if for nothing else, peace of mind.

You can do it yourself for an hour or so and the cost of fluid and some RTV. Got an oil drain pan..?

Are you the original owner?

I'm actually doing mine next weekend, front, rear diffs, T case. Gonna be fun!
 
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