DIY: changing the rear diff fluid

[strat81]

tools needed:
1/2" drive
breaker bar (may be needed to break the plugs loose)
1qt of 75/90w gear oil of your choice
oil catch pan

optional:
lift if you have access to one although it can be done with the car sitting on the ground
fluid pump (something to pump the fluid out of the oil container and into the rear diff. most autoparts stores sell these for around $5. while not necessary, it makes the job easier as there isn't alot of room to hold a bottle up to fill the diff)
1/2" torque wrench

step 1: with the car sitting on level ground, remove the upper plug from the rear differential using the 1/2" drive and/or breaker bar. although this is the fill plug, you should remove this plug first to ensure that you can get it out before draining all the oil out of the diff and then realizing you can't refill it.

step 2: with the catch pan under the rear diff remove the lower plug using the 1/2" drive/breaker bar and let the fluid drain into the pan.

step 3: once all the old fluid has drained into the pan, replace the lower (drain) plug and fill the rear diff with .8 qts or until the fluid starts to come out of the fill hole.

step 4: replace the fill plug and you're done.

torque specs on the plugs are 36.2ft-lbs but i just tightened them until they were snug. as for oil, i chose royal purple 75/90w synthetic gear oil but any 75/90w should work fine.

[Wiscon_Mark]

Thanks dude

[Huffer]

You forgot nose plugs because gear oil STINKS!

Also - for some lowered cars it's tough to get under the car when it's on the ground, so if you jack up the rear, put the car on jackstands then jack up the front so it's level (and put jackstands under that) it'll be easier to get under.

[ivwarrior]

Just 2 things to add (that I can thing of right now)

1. I'm pretty sure Subaru used 17mm drain bolts on a few rear diffs, just can't remember which. So, don't be suprised if you find them.

2. Doesn't the lower plug have a magnet stuck to/in it? It'd be a good idea to clean any gunk off it before putting it back in.

[strat81]

yes it does have a magnet... sorry forgot about that.

so far, i've only come across 1/2" drive plugs but i've only done two diffs (a 1st gen leggy and my wrx)

[tjpete04]

at what milage should this be done at would you guys suggest?

[filter27e]

Mine's a 17mm plug. I have a 98 2.2l auto, no idea what the rear diff is.

[Huffer]

at what milage should this be done at would you guys suggest?

Depending on levels of abuse - every 20-30k... if you autox, probably every race season (at least), as you'll cook the fluid quickly...

[warrior]

I used a small empty honey bottle to put the new fluid in the drain hole. It took a whole 5 min! You could also use an empty mustard bottle.. any bottle really with a tipped nozzle that is squeezable.