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Front & rear differential lube check


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I have been lazy, and never ever checked the lube level in my front and rear diffs. on my two Subbies. I know how to do it, but just how important is this to do? I don't see any lube stains on the diffs that would be caused by leakage, so I assume the lube level is okay. Opinions would be appreciated. Thanks Larry (Roooster2)

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honestly the rear diff is usually forgotten and I've seen many that have close to 300,000 on them and never been checked. I have only seen one ever go bad, and that was one that was rebuilt by someone that shouldn't have been touching a car! The front diffs probably should get checked. There's a dipstick to check the level, so its easy. And There would be a lot more wear on the front IMO. But if you don't see any leakage, they are probably just fine!

Edited by bratman18
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man if you dont remember the last time you even checked them.....If i were you i would prob. go ahead and change both of them...it cant hurt and its very simple to do.....

 

 

Is it a good idea to drain the gear oil from both diffs? Or, is it a matter of just topping off, if the oil level is a little low?

 

The last time I changed diff gear oil on my Audi,I used a synthetic 75W-90W. It was clear in color, and a little pricy. Is it advisable to use the synthetic in a Sub?

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lol.....funny question.

 

I dont think I would ever change the gear oil.....come on, they put that stuff in there, but its a subaru!

 

Ok...all sarcasm aside...yes, change it. Just like ANY differential, changing the gear oil out is pretty critical. Keeping the bearings cool, and clean is the oils job, and chances are, it needs changed. Dumb not to.....

 

I used 80/90 in my diffs, in my Legacy.

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+1 I would def. change it if you dont remember when you last did...I know Subaru recommends changing it every 30k miles....Ive drained quite a few diff's with some significant amounts of metal on the drain plug and some seriously dirty like almost black gear lube...

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The rear diff on my Sube has two plugs. One is a drain-plug, and the other is the fill-plug.

 

Remove the fill-plug FIRST, then remove the drain-plug and drain the oil.

Why? Because if you take the drain-plug out first, what do you then do if the fill-plug is seized?

 

The drain-plug has a magnet inside. Make sure to clean the iron-filings off of the magnet. When you see the stuff that is on that magnet, you'll know why changing the oil was such a good idea.

If I remember correctly, the two plugs have female square-holes, and I think that a 1/2" sq.drive fits into this (I'll check my car later, and edit this if I was wrong).

 

My rear diff takes 0.8 litres of oil (measured to the bottom of the fill-hole). You can make life easy for yourself, by buying a turkey-baster (the squeeze-bulb type). and using that to squeeze the oil into the fill hole.

 

The whole thing takes about 30-minutes.

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Thanks guys, the diff lube change is now on my "to do" list. It will be a while before I can get to it. It is still winter here in Indiana, so it will take some time before the outside temp gets into the 50's to do some comfortable work outside. Just one more thing to do.

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Many years ago while working at an Audi dealership, There was a recall campaign for the differential gear oil level on automatic 5000's. The purpose of the campaign was to check and fill the oil to the proper level. The reason was that to check the oil level it was a pain and in a hard to get to place, and no one ever did it. The oil levels were always low ( some VERY low ) with no visual signs of leakage. Where did the oil go? Would you believe that gear oil will actually evaporate over an extended period of time? I had never heard of this before, but was given this explanation by a pair of german engineers who had worked on the campaign. Whether this is true or not, I have found many differentials over the years that were very low , without any visible leakage!:-\

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the front diff is really critical. it's part of the transmission assembly so if it fails you're essentially looking at transmission replacement to fix it.

 

not worth such a huge job for a few dollars in gear oil.

 

and actually the front diff is really easy, its easier than an engine oil change. drain one plug and fill through the dipstick tube. just need a funnel.

 

so if you change your oil, you can do this. if you have a place do it for you, then changing the gear oil should be really cheap.

 

HEAT THE OIL UP before pouring it or it probably won't even go down a funnel, if it's cold. just keep the bottles inside until you're ready to pour.

 

i prefer synthetics but regular oil does quite well.

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