DIY: Rear Differential Oil Change

davidyan

Good write up. one recommendation for point #8 is that you should make sure that before plugging the fill hole, any excess overflow completely drains out. The fluid level should be exactly level with the bottom of the fill.

Also, since you used jack stands on the rear, not sure how level your car was. One way to avoid over/underfilling is to take measure the oil drained out and put the same amount back in. Take into consideration that about 0.1 quart may have stuck to the catch container.

spearfish25

There was certainly some tilt to the car but measuring the exact amount you put in will be darn near impossible. The siphon pump and tubing contain an unknown volume of oil, and there is no way to know how much you've cleared from the pump and tubing or how much is still contained within.

While the car was on the rear jack stands, I first took out the fill screw. No oil came out. Then I pulled the drain screw, drained the diff, replugged it, and refilled it. If anything there may be a bit more oil in the diff than when I started. One could always drop the car back to the ground, wiggle underneath and crack the fill screw to see if you drain any excess off.

I don't plan on doing that unless someone can convince me that 100ml too much oil in the diff will cause a problem. I've just driven 100 miles since the oil change and the diff is still working

***Just did some lurking in other forums. Looks like overfilling a diff can lead to oil leakage from the axle seals. It's usually solved by just emptying some oil out. However, people claim that jack angle won't allow you to severely overfill a diff. Mostly people have overfilling issues if they fill their diff while it's on their workbench and then reinstall it.

Modshack

My addendum to this in step 3 would be to ALWAYS do this first or at least make sure you can loosen it.! Reason being is if you can't get the fill plug out for whatever reason, and you've already drained the fluid you're sorta up a creek!

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spearfish25

Yep, I did just that but didn't put it in my original procedure description...you certainly don't want to have an empty diff and no way to refill it. That being said, it didn't take much force to break either screw loose initially. Original post updated to include this helpful tidbit.