gear oil in 250sx??

[mayhem17]

What oil do you guys run in the rear differential on these?

[Jmoozy27]

I use Lucas 80w gear oil. Never had a problem.

[oscarmayer]

I like the mobil1 synthetic.


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[mayhem17]

Just regular motor oil? Not using some sort of gear lube?

[Flyingw]

The manual specifies gear oil. I use Valvoline 80/90w gear oil. Fill to overflow.

[TheRealFatShady]

Some people run grease and say it keeps water out better, but I haven't myself.

[Flyingw]

Packing the diff with grease is a bad bad idea. There is a needle bearing on one end of the pinion shaft and the grease does not lubricate that bearing because the grease cannot get to the bearing. The large bearing at the other end of the pinion shaft also gets starved for lubrication. The diff is lubricated by a bath of gear oil. The bath splashes the oil throughout the diff lubricating all four bearings. The seal the propeller shaft slips in to is a water seal, not an oil seal but the initial protection for water entering the differential is the rubber boot that's between the engine and swingarm. If you want a water tight differential, ensure the boot is installed and not torn. Second is to ensure the propeller shaft end that slips in to the diff is smooth and corrosion free making for a water tight seal. Third is ensure the water seal is serviceable. If not or questionable, replace the water seal. The seals (2) on the ring gear are oil seals. If those seals are serviceable, water in the axle tubes will not get in to the diff. If you fill up the diff with oil and the oil leaks out then the oil is leaking out past the oil seals in to the axle tubes. Water intrusion in to the axle tubes is another problem entirely. Some guys swear by packing the diff with grease but I have seen first hand what happens to the diff when the needle bearing is starved for lubrication and its not pretty. At very least, replace the three seals on the diff and fill it with a quality 80/90w gear oil. Make sure the boot is intact and ensure the propeller shaft sealing surface is good.

[oscarmayer]

I should have clarified. Mobil1 synthetic gear oil.


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[Chopsaw]

The manual specifies gear oil. I use Valvoline 80/90w gear oil. Fill to overflow.

Overflow ? Out the fill hole ? I thought the manual said 3 oz. Maybe I need to fill it up .

[Flyingw]

Yes, out the fill hole. Some people including myself jack up the rear end to get a little extra oil in the diff.

[Jmoozy27]

Being that it isn't a high pressure part I say the more the better, just make sure your vent isn't clogged.