B8 A4: DIY Rear Differential Fluid Change

[Jmstrag]

I did the fluid change this week. I had someone look up the torque specs for the drain plug. Its listed at 45 nm or 33 ft/lbs. Thanks for the DIY write up.

[Demringstho864]

is royal purple any good for this. thats what i have always used in previous vehicles. or should i use something more German...

[Justin B8]

Just chiming in here.

Redline MT90 is not meant for use in diffs. You need an EP/extreme pressure rated gear lube in the diff. Something like Redline 75W90 gear oil.

[Mr_Skull]

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.

Any pics or details on a front diff fluid change? I have a B8.5 and assumed the front transmission and differential all used the same fluid. I'm getting ready to do the real diff and now learning I need to find out more about this front differential. Thanks!

[Demringstho864]

Where is the fill on a 09. I can't find it anywhere

[S4'ed]

The rear diff needs to use a GL-5 oil......

[s4baby]

Anyone have info for the front diff? Also where is the fill plug for 2009's?

[Dr. Awesome]

is royal purple any good for this. thats what i have always used in previous vehicles. or should i use something more German...

Royal Purple should be fine, it's GL-4 and GL-5 rated. I'm no oil expert, but the specs are all there. I have some in the garage already so that's what I plan to use.

Anyone have a suggestion for a good syringe to fill this? Maybe one that would work for a transmission fill, too?

[Spawne32]

Im using redline 75w90 gear oil which is GL-5 spec as audi recommends this weekend, 90k on the fluids (just bought the car). Wouldnt run a manual trans fluid in a differential IMO just like someone said. Differentials tend to be extreme pressure environments and require friction modifiers regardless of whether they are LSD or not, has to do with the way the gears mesh. No syncros in diffs as well which is something they take into account with the manual trans fluid.

[Mr_Skull]

I found this in another thread related to the front differential service on the B8.5 model. I'm planning on using GL-5 Synthetic 75W-90 on the front and rear. Now I'm curious about this center differential I'm reading about and what type of fluid it may utilize.

On my 2014 the front diff has a small drain plug on the bottom of the housing. The fill plug is on the side behind the axle. You can access it through the wheel well and sliding the wrench and fill hose past the heat shield. The drain plug uses a 5 mm allen and the fill plug is an 8 mm allen.

The center diff appears to need to be siphoned out. I did the rear and front and will do the center some other time. I am using Amsoil on the front and rear, but they don't list a product for the center.

The Amsoil website says they all take 2.1 pints. The front diff drained out of the fill plug when I pulled it so I take it you just top it off.

Edit: Found this in another thread related to the center differential.

The center diff has Sturaco friction modifier added to the standard 75-90 fluid, to reduce stress in the limited slip diff. It's expensive at the dealer. I have read that it isn't required unless replacing/rebuilding the diff, but can't confirm if this is true. I asked ZF and they were vague, suggesting that I use the OEM fluid. So, I will take the conservative approach and buy the dealer fluid....probably $60/l vs $20 for the gear oil only. Since it's small $$ and a long time between changes, not worth it to risk it IMO. If the friction modifier is not sufficient you will get some noise or shudder with tight turns.
There is a drain plug on the center diff, but you need to drop the trans support to access it. The fill plug on the side is also not easy to get to. I have done the front and rear but haven't tackled the center yet. The next time I'm under the car I will look more closely at the room available for the fill plug and getting a tube in there to extract the fluid.

[Spawne32]

Did the diff fluid change today, fluid was surprisingly clearish coming out and seemed to be in relatively good shape, had some sparkly metal in the fluid which apparently is not uncommon. I don't have a lift so getting the car level is next to impossible so I went strictly by fluid capacities, drained a hair under 1 quart and pumped a quart of redline gear oil in which is NOT red in color, it is the same color as stock. Put some thread sealer on the plugs and hand tightened them, had to use a 8mm allen key on the drain because it sits behind the diff mount. Ill try to get a pic of the condition of the diff oil that came out.

[JBAeroEngineer]

Is there a DIY for the seals? Mine are leaking at the input shaft.

[jfo]

Is there a DIY for the seals? Mine are leaking at the input shaft.

Sent you a pm

[SleeperCar]

My car has 61k miles and I haven't touched this fluid....

Hmmmmm

[A4x]

My car has 61k miles and I haven't touched this fluid....

Hmmmmm

I'm at 70k miles and havn't touched it as well. Planning on doing this in the next few weeks. Just decicing on what fluid to go with.

I really like the Liquid Moly engine oil, so I might try their 75W-90 GL5 gear oil. Anyone have experience with this?

[Dr. Awesome]

I just did this yesterday, my drain plug was on the rear of the diff instead of on the bottom (2012 A4 2.0T Quattro). It should be noted that the drain plug is very shallow as far as clearance goes, I ended up having to use a 90 degree 8mm allen wrench on it and a little cheater bar to get it off, which means I couldn't torque it when I re-installed, so I just tightened it down using a little less force than it took to get it off. The fill plug is easy with an extension and an allen wrench socket adapter, you just have to go over the top of the exhaust (though I have aftermarket, so I'm not sure if stock interferes). I used ramps on the front and jacked and supported by the pinch weld in the rear in order to get it nice and level. This is important since you are filling it until it flows out.

I used Mobile 1 75W-90 GL-5 with a cheap hand pump off Amazon. I flushed it out a bit with since I could see some of the tiny metal flakes washing out, ended up using about 1.5 quarts. I'll probably do it again in 40-50k, maybe sooner if I run out of other things to do!

[KILLzombi3z]

Hey op, pics don't show.

[cuda2000]

New DIY Videos!!
1. Rear Differential Gear Oil video:https://youtu.be/RLyTP5qIRQk

2. Front Differential Gear Oil video:https://youtu.be/xwD-gGGTyfE

3. Transmission fluid and Center Transfer Case oil video:https://youtu.be/IY_VRHlfJuQ

Sent from my LM-G820 using Audizine mobile app

[Smac770]

Only speaking for US spec info, there's the 0BC and 0BD rear diffs on our B8 A4 2.0T quattros. For the ZF automatic vehicles, it's 0BD-KBU and 0BC-KRR (3.308 ratio with 70.7mm flange). Manual vehicles appear to all have 0BC, with different stats than for the ZF, thus different diff code. 0BD has the drain plug on the lower backend. 0BC has the drain plug on the bottom.

0BD-KBU, fill/inspect and drain plugs are the same, part number 0AA 409 057 (M16x1.5, 8mm inner hex), torque spec 45Nm.
0BC-KRR, fill/inspect and drain plugs are the same, part number N10 037 105 (M22x1.5, 10mm inner hex), torque spec 30Nm.

Guessing it's 10mm due to the first post; I have a KBU myself. No idea why the difference in torque spec, but that's what's printed in the Audi repair manuals, so that's what I'm typing here.

I did not replace my plugs. Just cleaned them and oiled the o-rings with the new oil. Hope it doesn't turn out to be a mistake.

For torquing the drain plug, it was pretty simple. For the fill plug, I had the torque wrench with a 15mm socket and 8mm hex stubby (from the GearWrench 81550 set) and that worked great. I was going to use that stubby with a crow foot for the drain plug, but crow foot is just too short for any use there. In place, I put my 8mm hex key back on, put my 8mm wrench on that (on the part sticking into the plug, not the handle sticking down) and then put the torque wrench with the 8mm stubby on the other end of the wrench. The wrench added 4" to the effective lever length, increasing my handle center to rotation point from 15" to 19". I had to adjust my torque setting: 45Nm / 19" * 15" = 35Nm. Easy enough.

It would be really nice if someone out there made some metric sized (8mm-19mm) 3" long 3/8" drive torque adapters. I'm sure they would try and charge too much for them, so wrenches and hex bits it shall be.

So this is what 201k miles old rear diff fluid looks like:

rear diff fluid after 201k miles.jpg

[ps2cho]

I just replaced my 2016 Allroad's rear differential fluid...Only strange thing is that I got 800ml drained out, yet I filled about 950ml...

Could it have been underfilled at the factory potentially? Fluid was very clean, no metallic shards. Car was filled until it came out the top fill port...Didn't even jack up the car since its the Allroad, so it was definitely level.

Sort of odd.

[A4x]

Could have had some of it leak out over time. Take a look at the pinion and diff side seals for signs of weepage.

[LmG7119]

Is there a schedule when you need to do those or you guys are doing it just because( for low mileage cars)?

[clettngx]

Why does the MT-90 oem chart list the part number for the rear diff oil, yet it's not gl-5? I've just got some.based on this, but now I read it's not gl-5! FML

Sent from my MHA-L29 using Audizine Forum mobile app

[Skribbles505]

All 3 videos really helped me with this yesterday. Really glad a community exits with posts like this! Unfortunately the front diff fill stripped so I still need to get that out and broke the center diff drain plug when I tightened it so I'm waiting on new ones to arrive. 168k and it's probably never been done before.

[JSIL1]

I know I'm dredging up the dead, however, what about Amsoil 75w90 Severe Duty for the rear diff?

its product sheet shows GL5

[Smac770]

If it's a 75w90 GL5, I imagine it'll be fine enough. I don't know what their Severe Duty tag implies or if it's necessary for a car. But I can't see it being problematic.

[JSIL1]

If it's a 75w90 GL5, I imagine it'll be fine enough. I don't know what their Severe Duty tag implies or if it's necessary for a car. But I can't see it being problematic.

That is what I was thinking.

They have a 'normal' version 'Long Life Synthetic' that is GL5 rated as well, I was just leaning towards the Severe Duty because I track it occasionally and drive it pretty hard.



EDIT: I just got off the phone with a gentleman named Darren from AMSOIL and he confirmed that I want to use the Severe Duty version. The Severe Gear is designed for non-commercial vehicles while the long life product is for large trucks and OTR heavy-duty applications. It is based off the fact that consumer vehicles have a sump in them and a lighter load demand. Long Life is for trucks with massive sumps and extreme loads. TIL.

[cincyadam]

Aside from the ATF fluid change on CVT cars, I’m not seeing anything on the Audi maintenance schedule regarding the differentials. Anyone have info on the intervals?

[JSIL1]

This is from my local Audi dealer.

They only call out the RS5/7 and the R8, however, ounce of prevention.....

First change at 40k mi, and then every 40k after.

https://www.prestigeimports.net/serv...nd-procedures/

I just changed my fluids, I had Fuchs in Diff and Audi in my MT, not Redline MT-90 and AMSOIL 75w-90

Transmission has about 60K. Diff has about 45K

Fluids - Diff - LEFT MT - RIGHT

[Chillaxin]

Reviving this thread from the dead. I'm looking to centralize some information about front/rear diff fluid (NOT CENTER DIFF). All of these are 75W90 Synthetic.

Amsoil Severe Gear GL5 Viscosity@40C 97.8 cSt, Viscosity@100C 16.0 cSt, Pour Point -43C, Flash Point 222C

Amsoil Long Life Gear GL5 Viscosity@40C 115.8 cSt, Viscosity@100C 15.7 cSt, Pour Point -48C, Flash Point 208C

Liquid Moly Hypoid Gear Oil GL4/5 Viscosity@40C 106.0 cSt, Viscosity@100C 15.6 cSt, Pour Point -50C, Flash Point 200C

Liquid Moly HP Gear Oil GL4+ Viscosity@40C 81.5 cSt, Viscosity@100C 14.3 cSt, Pour Point -60C, Flash Point 200C

Redline GL-5 Gear Oil Viscosity@40C 108 cSt, Viscosity@100C 16.1 cSt, Pour Point -45C, Flash Point Not Listed

Redline MT-90 GL4 Viscosity@40C 82 cSt, Viscosity@100C 15.5 cSt, Pour Point -45C, Flash Point Not Listed - This is what redline's website recommends for F/R Diffs for B8 A4 with ZF8speed.

After looking through all of these, the best oil for fuel economy would be the LM GL4+ available from FCP. The automatic doesn't produce high shock loads or extreme pressures of a non-tracked car mostly used for commutes. This benefit would be amplified in cold weather and short trips. If I were to track or race, or had a manual that did launches, that would be a different story.

I wasn't able to find any datasheet for the OEM fluid G052145S2.

I just did some digging around and thought I'd share this info for anyone looking.