Questions on 5eat Diff fluid change.

Have searched, but most posts on the topic are a couple years old, and some contradict eachother. I've already had a tranny fluid drain fill done, I want to do the front and rear diffs.

 

1. What type of oil should be used for the diffs, and should the same be used for the front and rear? Is the general consensus to use Extra S gear oil? My dealer told me they use some GM brand 80/90 oil. (They are tied in with a Cadillac dealer) They said that any 80/90 oil that was (GL5?) would do. Don't know if it makes a difference, but I live near Cincinnati. Winter temps can reach sub zero and summers can reach 100*.

 

2. I've seen the pictorial guide for changing the rear diff, but does one exist for the front diff, or atleast a text walkthru?

 

3. If Extra S is what should be used, can it be bought by the quart now, or do you still have to buy the large container?

 

4. I believe the rear takes about a quart, but how much oil do you need for the front diff?

Here are my notes.

http://legacygt.com/forums/showpost.php?p=2572048&postcount=164

 

You need the same fluid in the front and rear differentials. 75w90 (NOT 75w90NS)

I went with Amsoil because it was the same price as Valvoline, Mobil 1, Pennzoil, etc. Just find a local dealer so you don't pay shipping and go get yourself 3 quarts of Amsoil 75w90 Severe Gear. It's very good stuff.

Front diff:1.4-1.6 quarts

Rear diff: 0.8 quarts

You will need a T-70 torx bit for the front differential.

Extra S is good stuff. It can be purchased in quarts from fredbeansparts.com.

See the attached PDF.

Depending on what type of rear differential you have, you will either need an Allen wrench (14mm?) or a 13mm square socket/half-inch drive.

Get yourself 3 crush washers from the dealer, two for the rear, one for the front. They are NOT the same size as the oil crush washers, they are a bit narrower.

 

Does anyone know if the automatic transmission Legacies come automatically with one type of rear diff or the other? Mine is a VA2 so I am lucky I don't have to mess with half-inch drives not matching perfectly the 13mm square socket.

Front & Rear Differential Gear Oil Replacement.pdf

Thanks for the info guys.

Any idea why my dealer would say to use 80/90 oil and not 75/90?

Because that's what they have a bunch of in stock and trying to get rid of it.

The owners manual specifies the viscosity of diff fluid. It is not always 75w-90. I should also mention that Amsoil Severe Gear is overkill. I think that stuff wouldn't shear on a 24hour track race even if the race was in Death Valley. I chose Amsoil regular 75W-90, will be going thicker when TX summer comes through.

^I agree that it's overkill but again, for the fact that it cost me the same amount it would have by going with any of the other off the shelf offering, why not

are there any drawbacks to going with overkill oil?

ahhah no ! synthetic 75w90 is nice for cold .. when you put he car in gear and it doesn't want to move on its owm with 80 w 90! in texas your fine with 80w 90 canada its nicer to have the synthetic. but you guys realy have to stop obsessing about oil grades ! i get what ever is on sale !

Stop obsessing!!!!!!

 

That will never happen

stop obsessing!!!!!!

 

That will never happen

 

never!!!

Does anyone know if the automatic transmission Legacies come automatically with one type of rear diff or the other? Mine is a VA2 so I am lucky I don't have to mess with half-inch drives not matching perfectly the 13mm square socket.

 

 

As far as I know the Auto always came with the VA2 rear diff.

I like the VA2 better than VA1. No messing with half inch drives that aren't quite 13mm. Close, but not quite, lol.