DIY: B6 A4 - Change Your Rear Diff Oil

[Saturnine]

Just finished this a few minutes ago, just thought i'd share how I went about it..

One a scale of 1-10 (1 being easy, and 10 being hard) I'd give this "mod" a 2-3.. Hardest part is jacking up the car and putting it on jack stands.

Tools/Supplies Needed:

10mm hex socket
3/8" socket wrench with a decent amount of extensions (No more than 12")
1.5L of your diff fluid of choice (I recomend Motul's Gear 300 SAE75w90)
Hand Pump
Bucket to catch old diff fluid
Jack+Stands
Rags

Step 1: Jack up car via the rear diff mount and place stands on either side of the car (Or use a lift if you have access)



Step 2: Locate the 10mm hex bolt drain plug. Its super easy to find, its the only bolt on the bottom of the diff near the drive shaft



Step 3: Using your socket wrench, losen the drain plug and let contents drain into bucket etc..



Step 4: Replace drain plug

Step 5: Locate the 10mm filling plug and losen.. Its located on the right side of the diff towards the back of the car (Plug faces the right rear wheel)



Step 6: Using your hand pump, pump in about 1.5L of gear oil.. If you had a crappy hand pump like mine, it should only take about 10-15 mins to fill the diff. You'll know the diff is full of fluid, because it will start to dribble out of the filling plug. (I also recomend keeping track of how much you've pumped in via the scale thats on the bottle)



Step 7: Replace filling plug and check to make sure both the filler plug and the drain plug are tight.

Step 8: Wipe away any spilled gear oil and your done!

I will be changing my tranny fluid tomarrow, so look for another write up!

[CuStOm]

Good Job!
I've totally been thinking about doing this. I have a couple of questions:
Is the rear diff factory filled with synthetic?

What about the center diff?

You say you are doing your tranny, do you have an MT? Are you gonna do a write-up on it also? What fluid you gonna run there?


Thanks for your time!

[Saturnine]

Yea, the factory rear diff oil is apparently a synthetic of some sort.. The center diff fluid is shared with the tranny fluid, and i will be using the same Motul as i used in my rear diff.. I do have a 5 speed..

I would like to do a write up on changing the tranny fluid, but i looked at the drain plug last night and its a super weird bolt that ive never seen before.. It looks like the multi-pointed torx bit that are used for the head studs, but it has a a little bump in the middle.. Hard to explain, but in sort i dont have the bit for it so i'll have to go hunt one down..

[Gallep]

It looks like the multi-pointed torx bit that are used for the head studs, but it has a a little bump in the middle.. Hard to explain, but in sort i dont have the bit for it so i'll have to go hunt one down..

Sounds like a Tamper-proof Torx.

[quattroism25]

Just thought I'd add...Before you pull the drain plug its best to loosen the fill plug first. You don't wanna drain the oil then find that the fill plug is stuck, stripped or whatnot, then you'll really be fvcked.