B8 A4: DIY Rear Differential Fluid Change

[Dan_Q]

You’ll need minimal mechanical ability for this one and 1+ qt of the proper gear oil. This is even easier than changing your oil.

I used Redline MT-90 75W/90 Synthetic fluid.



Step 1: Get the car up levelly on four jackstands . You need the car level in order to fill the diff properly.

Step 2: Remove the fill plug (red) using a 10 mm allen. Remove the drain plug (blue) using an 10 mm allen as well. Always remove the fill plug first, because if you open the drain plug first and the fill plug ends up being stuck then you’re F’d.



Step 3: Drain the fluid into a pan.



Old fluid wasn’t looking too good (This is actually my trans fluid). I took a pic of the diff fluid as well but it looked identical. I labeled the fluids in the photo so you can tell the difference. Very tough to tell the difference at first glance.



Step 4: Once empty, reinstall the drain plug. This is the only car I’ve ever owned that didn’t have a crush washer on these plugs. I have no idea what the torque is but I torqued it to 32 ft-lbs. Seems about right for this size bolt.

Step 5: Pump fluid into the diff through the fill hole. I use my trusty syringe which holds about a half qt of fluid.



Step 6: Keep filling until you get a steady stream of fluid draining out the fill hole. Mine took just over 1 qt.

Step 7: Reinstall the drain plug (again no crush washer). Again I have no idea what the torque is but I torqued it to 32 ft-lbs because that seems about right for this size bolt. This is obviously a non critical bolt and torquing it is good practice but not all that critical. I spray everything down with brake cleaner when I'm done so that if a leak ever happens it will be evident.

Step 8: Lower the car if you’re done.

I do this on all my cars every 30k miles. Audi recommends never doing it and says the stock fluid will last the "lifetime" of the differential. Of course the "lifetime" of the differential will be severely shortened if you never replace the fluid. If you do it every 30k miles it will basically last forever. Total cost for 1 qt of synthetic fluid is about $8-9. Not sure what the cost of a new differential is for sure, but it seems it's probably more expensive than a quart of gear oil every 30k miles.

[jbradle7]

Good info, thanks!

[eyrah]

excellent! now i have something to do on sunday, you need to come up with one of these ever week until football season starts please and thank you.

[simplicity]

delete - double post.

[simplicity]

Very nice! I noticed you were able to get jack stands on the jackpoints pretty much spot on.......where did you place the jack to get all 4 stands in there?

I think the torque specs are 26lb/ft for the drain plug and 13lb/ft for the fill plug (per a DIY for B7RS4 rear diff change)

[yma4]

Thanks Dan-Q! Great DIY....definitely doing this next weekend :)

[SMH]

Great DIY! Doing this for sure!

Love the syringe to!

[jfo]

Thanks Dan. Is there a spec for this fluid if Redline isn't available, and do we assume the rear dif is the same for Tip transmission?

[TCHUN003]

I love you Dan. Beer + DIYing is so fun when you have pictures/instructions lol.

Thanks Dan. Is there a spec for this fluid if Redline isn't available, and do we assume the rear dif is the same for Tip transmission?

I'm interested in this as well

[TheHeiko]

I love you Dan. Beer + DIYing is so fun when you have pictures/instructions lol.


I'm interested in this as well

I'm only at 30K miles now but do I sense a fluid change day at Jaysen's? We could buy some Redline bulk and save some dough.

[TCHUN003]

I'm only at 30K miles now but do I sense a fluid change day at Jaysen's? We could buy some Redline bulk and save some dough.

Your spider sense is pretty accurate because that's what's going to have to happen. Brady should come too. I'm always down to buy in bulk and save some dough!

[yma4]

Your spider sense is pretty accurate because that's what's going to have to happen. Brady should come too. I'm always down to buy in bulk and save some dough!

I'm in! Tell me when gents

[Highlander1010]

Much appreciated Dan. I'm going to be in DIY heaven when I get home in a few weeks. EC Pulley, Fluids and the Rear Diff mount.

[Dan_Q]

excellent! now i have something to do on sunday, you need to come up with one of these ever week until football season starts please and thank you.

Oh don’t bring up football! We just picked up Wes Welker and it is all I can do not to think about it every 5 min. Since you’re in SD, I hope you’re not a Charger fan. Because they won’t have a shot at winning the AFC West until Peyton retires!

I noticed you were able to get jack stands on the jackpoints pretty much spot on.......where did you place the jack to get all 4 stands in there?

I’ve got two floor jacks. I start out by putting one on where each of the Lower Control Arm Bushings connect to the frame to lift the front up. If you only have one jack you could lift one side then get a jackstand in its lowest setting under that side. Then swap to the other side and do the same thing. Then repeat to get up to full height.
For the rear I just stick a block of wood on the jack to distribute the load and jack from the rear subframe.

I think the torque specs are 26lb/ft for the drain plug and 13lb/ft for the fill plug (per a DIY for B7RS4 rear diff change)

13 sounds really low for a bolt that large but maybe. The bolts are big enough that 32 ft-lbs certainly isn’t going to strip them. But like I said, it isn’t a critical location so “tight” is probably tight enough.

Is there a spec for this fluid if Redline isn't available, and do we assume the rear dif is the same for Tip transmission?

Any 75W/90 gear oil should work. That is the weight of the factory fluid which runs about 8X the cost and is no doubt is inferior to a high end synthetic. The diff should be identical on an automatic. The only diff that is substantially different is the optional sports diff on the S4. And I'm sure that one takes a different fluid.

[TDIaholic]

Redline shockproof heavy is better for the rear diff than MT-90. Nice DIY though! I need to do mine too next time I change the oil.

[Bezlar]

Oh don’t bring up football! We just picked up Wes Welker and it is all I can do not to think about it every 5 min. Since you’re in SD, I hope you’re not a Charger fan. Because they won’t have a shot at winning the AFC West until Peyton retires!
.

Stop it. How did that playoff game go for ya. My chiefs will have somthing for ya soon.

[Highlander1010]

Redline shockproof heavy is better for the rear diff than MT-90. Nice DIY though! I need to do mine too next time I change the oil.

Why is Redline shockproof heavy better? Just for education's sake.

[k9lovr]

Stop it. How did that playoff game go for ya. My chiefs will have somthing for ya soon.

Oh wishful thinking...Go Broncos!!

[k9lovr]

Much appreciated Dan. I'm going to be in DIY heaven when I get home in a few weeks. EC Pulley, Fluids and the Rear Diff mount.

Im in the same boat....

[simplicity]

I’ve got two floor jacks. I start out by putting one on where each of the Lower Control Arm Bushings connect to the frame to lift the front up. If you only have one jack you could lift one side then get a jackstand in its lowest setting under that side. Then swap to the other side and do the same thing. Then repeat to get up to full height.
For the rear I just stick a block of wood on the jack to distribute the load and jack from the rear subframe..

Thanks, I might drive the front up ramps and then jack the rear at the frame underneath the rear diff.

[Highlander1010]

Thanks, I might drive the front up ramps and then jack the rear at the frame underneath the rear diff.

That sounds a wee bit risky. The car would want to be coming back down the ramps towards you. You can block the back wheels to help I suppose.

[TDIaholic]

Why is Redline shockproof heavy better? Just for education's sake.

The shockproof heavy has EP additivies, which makes it behave like an oil with higher viscosity when it comes to film thickness. It doesn't work well in the trans as it's not really compatible with synchros.

[Highlander1010]

The shockproof heavy has EP additivies, which makes it behave like an oil with higher viscosity when it comes to film thickness. It doesn't work well in the trans as it's not really compatible with synchros.

Interesting. Do you know of anywhere to read up more on this?

[k9lovr]

Just wanted to update this thread....2009's have different differentials in the rear as I just completed this and the drain and fill plugs are on the drivers side of the differential and the bottom looks different. You will need a swivel and extension to get over the exhaust to remove the fill plug. Here are a few pics I took.....

[nikatrel]

So do we have a confirmation it is the same oil on an auto as a manual?

[TDIaholic]

The rear diff oil is always the same regardless of transmission. The Sport diff could be different, I'm not sure.

The only difference between the manual and automatic oils is that the auto tranny has its own oil, and the torsen center diff has its own oil, where as in a manual tranny the center diff shares the transmission's oil.

[Alipapa]

great info!!!

Do we need to change the front diff oil as well, or it shares oil with the transmission?

I have been struggling to find DIY write up for the DSG oil change...

[feistyfoo]

What about the seals that are included in the ECS service kit?

http://www.ecstuning.com/Audi-B8_A4-...Kit/ES2593489/

[feistyfoo]

What about the seals that are included in the ECS service kit?

http://www.ecstuning.com/Audi-B8_A4-...Kit/ES2593489/

Did any body replace them?

[TDIaholic]

Don't touch the seals unless they're leaking. I'm not sure why ECS includes them in the kit as 9 times out of 10 you don't need to replace them when replacing the diff fluid.

[oascom]

Well.. Ordered this Redline MT-90 75W/90 Synthetic fluid and will try to change it.

Now only need to change Trans fluid...

[feistyfoo]

Dumb question... Should the front differential fluid be changed too? Is it possible? In my old Touareg, the procedure was practically the same for the front and rear.

[TDIaholic]

If you have a tiptronic transmission then the front diff has its own oil. If you have a manual the diff and trans share the same oil.

[feistyfoo]

Cool. Thanks for the info. I saw the kit for the front on ECS so I didn't know.

[jfo]

After looking at Redline's web info, I have a question about MT90 use in the rear dif. Audi calls for GL-5 oil in the rear dif. Redline's application guide suggests MT90 for both the manual trans and the rear diff. MT90 however is GL-4 grade, which is required for the manual trans but not the rear dif. The MT90 product details then says MT90 is "not for use in differentials with hypoid gears" Isn't our rear dif a hypoid gear system? I wonder why Redline doesn't suggest their GL-5 gear oil for the rear dif?

[TDIaholic]

GL-5 is one of the reasons why I'd recommend Shockproof Heavy instead of MT-90. The higher the GL number, the more additives it has. Myself, I would not use MT-90 in the rear diff.

[Mina08]

I will changing the rear diff oil tonight and i will be using this, will also post some pics



Sent from my iPhone using Tapatalk

[Mina08]

Got it done last night takes 20mins, also did the B6

[burbs9]

At what mileage are you all changing the differential fluid??

[s4baby]

Just wanted to update this thread....2009's have different differentials in the rear as I just completed this and the drain and fill plugs are on the drivers side of the differential and the bottom looks different. You will need a swivel and extension to get over the exhaust to remove the fill plug. Here are a few pics I took.....

Which one is drain and which one is fill?