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03 Explorer XLT: Driveline fluid changes

04-11-2018, 03:30 PM
140k on 03 XLT and I'm ready to change driveline fluids.

Transfer case: It appears 1.5qt of Mercon. I've seen cautions against using Mercon V...to be sure the fluid is safe for transfer case. Still true?

Rear differential: 3.55 non-limited slip 8.8" (code 45): The manual says fluid is for "life" and doesn't need to be changed, but I'm skeptical. Proper fluid is synthetic 75W140 with "friction modifier" - correct? How much friction modifier?

Front differential: 80W90 - right? No friction modifier - right? Does it have to be synthetic? (I already have conventional 80W90 in garage.)

04-12-2018, 05:53 PM
The Mercon V is synthetic version of Mercon, great for transmissions built with the proper seals, but bad for everything else.
I can't comment on synthetic gear oil, I've always used standard. I know some racers swear by the synthetic, but they aren't going 100,000 miles or more between changes.

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