Yes - if the three following conditions are met, then diff failures are RARE
- proper spec fluid is used (typically a fairly wide range of acceptable vis and base stocks will work)
- proper ring gear and pinion set up for contact pattern, backlash, etc
- proper light break-in before heavy use, to burnish the ring/pinion relationship
If these are met, diffs are almost a fill and forget thing. And while that scares the Hades out of most BITOGers, the reality of anecdotal proof is in the scad-zillions of vehicles that see hundreds of thousands of miles of use and yet have few failures.
I generally will run easy application use for about 1k miles on a new vehicle, change the diff fluids to flush out the break-in stuff, and then leave them be for at least 100k miles before even considering an OCI for heavy applications, and 150k miles for light applications. I might check the fluid levels every other year or so, but I don't change the gear lube until at least 100k miles has gone by.
Case in point: my wife's former 2005 Grand Marquis with FoMoCo 8.8 diff. We got it used with 157k miles on it. I serviced all fluids which included the rear diff fluid; it surely looked to be the OEM fluid and there was no written or physical evidence that it had ever been changed in that first 157k miles. When my son and I pulled the diff cover, the fluid looked "iffy", but the ring/pinion and spider gears were perfect; the unit was still nice and tight with no abnormal wear anywhere and the contact pattern was text book perfect. After installing some dino 80w-90 and running the car another 110k miles, the car has recently been sold to a friend who continues to drive it daily. I told him he might want to change the fluid again since it's been 110k miles, and he said he might, if he gets around to it. But honestly, at some point, what is the point? Diffs don't get contamination as long as they are not submerged and the axle vents work well. Wear is normal on any mechanical device. The unit is so well burnished that overly anxious OCIs probably are not going to alter the seemingly limitless lifespan of the diff. It's a 4.6L equipped, 8.8" 2.73 geared vehicle that sees "normal" use. As a species, cockroaches are the only other thing I can think of which hope to live as long as those cars can run.
For your F-53 Dana, I think you should take a UOA once another 10k miles has elapsed. Then you can probably push the next UOA out to 25k miles, then after 50k miles, and then at some point, you'll just either forget or get bored, realizing it's moot ...
