I am using mobil 1 75w90 in both front and rear diff. 2 bottles will do, .o8 in the rear and 1.3 in the front. (4eat)

 

If a manual trans, use only a straight 80w90. If using a synthetic 75w90 in a manual trans, it MUST be synchromesh for bronze parts AND gl-5 rated for the front diff. Subaru extra-s recommended or any synchromesh fluid with a gl-5 rating. Most of these synchromesh oils will be gl-4 rated which is not appropriate for the diff in the manual trans

Edited January 8, 201511 yr by MilesFox

i was thinking to use valvoline 80w90 non synthetic for front diff/tranny and valvoline 75w90 non synthetic for the rear diff

Both a 75w90 and an 80w90 are still 90 wt oil at load and temp. the 75w will flow better when cold (northern climate) and may be better for your fuel economy. This is my logic when using a 75w90 over an 80w90 in my application where it calls for 80w90 all temps or straight 90 for hot climate.

Edited January 8, 201511 yr by MilesFox

Ah ok. I knew it wasn't a big difference but never experienced it myself So figured I'd go with OE recommendations but I'll go with the word of experience and do 75w90 all around. Gonna be doing it Saturday so hopefully weather isn't too cold

TIP:

on the rear diff,

remove the fill plug, top one, first.

i you can not get it out,

do not drain the diff.

yeah i had read that haha are they really that bad to get off?

any other tips besides 1/2 with a penny and some PB?

mine were.

and there are lots of busted socket, breaker bars and bent jacks to prove it.

 

the problem is ,

unless the car is at least 2 feet in the air.

you cannot swing the breaker bar.

when the guy at my shop did mine,

i think he used a 3 ft. breaker bar.

awesome. I used a hydraulic jack like so with a ratchet and it came out just fine:  http://imgur.com/wWqdoHe

 

thanks team

I just replaced the oil in the rear diff on my 1992 legacy wagon and used  an old 1/2 inch ratchet and jack to remove plugs.  Maybe just lucky but no problems.  I used the Redline 75/90 synthetic that so many recommended.  I was going to change oil in the front diff but when I pulled the little dip stick that is on the right side near firewall it has the red ATF fluid on it.  I have the auto trans and thought that the diff would also use the 75/90 oil.  I'm sorry but I am a 80 year old idiot and have a problem trying to sort out some problems.  My Subbie that I bought used 15 years ago just turned over to 137000 and I try do my own maintenance. Following directions in the Haynes Repair Manual I found the drain plug for the front diff but I don't if I want to drain it until I find out what oil to use.  Does the auto transaxle share oil with the diff?

The front diff dip stick is on the passenger side. Way down there on the transmission.

 

The drivers side is the atf.