Differential maintenance

[9milecanyon]

I recently purchased my first diesel, a '99 and am trying to make sure all maintenance issues are up to date. It's got 152000 miles on it. What do you recomend for differential gear oil?

[NCHornet]

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[SmokeyWren]

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What do you recomend for differential gear oil?

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Ford now says you should use synthetic 75w140 gear lube in the rear axle of any '99-up SuperDuty pickup. It doesn't matter which brand, as long as it's synthetic and is 75w140. Motorcraft brand is good stuff. So is Mobil 1, Redline, AMSOIL, and several other brands.

When your pickup was new, Ford was requiring 75w140 synthetic in the rear axle of pickups with single rear wheels (SRW), but synthetic 75w90 in the pickups with dual rear wheels (DRW). But recently Ford decided that 75w140 synthetic was best for the rear diff in all SuperDuty pickups.

If your pickup is a 4x4, then it requires a different axle lube in the front diff - 75w90 synthetic or straight 90w synthetic. The key is synthetic. Don't buy the cheap stuff that is not synthetic.

If you don't have a handy source for synthetic gear lube, then I recommend you order what you need from Bob Riley at click here. Note that AMSOIL makes both the 75w140 for the rear end and the 75w90 for the front end.