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Sport Differential failure! help/options?

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Old 01-10-2018, 11:31 AM
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Default Sport Differential failure! help/options?

Hi, all:

I was driving my manual S4 on the highway in a straight line, then slowly braked at a service station. The sport diff light came on. I had made no sudden turns, or stops and was not driving aggressively. I got to my destination, then an hour later, turned the car back on and the diff light went away. My mechanic cleared codes 0334/C1005 - "oil pressure and temp sensor 2 G640 implausible signal." He removed the sensor, applied contact enhancer and erased the fault.

The fault remained sporadic but kept coming back on. He then replaced the #2 sensor and topped off the diff. fluid. After doing that, the code came back immediately and the diff light has been lit ever since. He said the new sensor needed to be "adapted to AWD control module J492 by the dealer due to scan tool security access restriction."

So, I took the car to my local Audi dealer. They told me there's nothing to adapt with the sensor. They ran diagnostics, cleared the code and of course, it came right back. They're now telling me I need to replace the entire rear sport diff.

I see no fluid leaking, hear no whining noise and sense no performance issue that I believe would accompany a rear diff failure.

The dealer says they will install either an aftermarket diff or a salvaged one from a wreck if I can find one. So - what's the consensus? Does this sound like a rear sport diff failure? If it is, is the part I need 0BF500043Q? Can my mechanic install it or do I need to have it done by Audi? Any relevant TSBs? Thanks. Hoping for the least worst options at this point.

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Old 01-10-2018, 12:59 PM
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Have you had a gear lube analysis done yet? It would tell you if there were metal particles in there. Has fluid been drained and closely examined? I for one would not leap into replacing anything!
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Old 01-10-2018, 01:17 PM
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What would happen if you did nothing? Would the dif work without vectoring? Dealer will charge you much more to do the job than an independent mechanic.Labor rates are so much higher.
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Old 01-10-2018, 01:24 PM
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Here is a thread that discussing the same fault codes that point to the B8 S4 Sport Differential failure: Sports Differential System Fault

It seems that the problem stems from a leak in one or more seals. There seems to be a Technical Service Bulletin for this issue. You can read it here: Sport Rear Differential Oil Leak - Known Issue? - Page 6
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Old 01-10-2018, 01:24 PM
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Originally Posted by Stevereddy View Post
Have you had a gear lube analysis done yet? It would tell you if there were metal particles in there. Has fluid been drained and closely examined? I for one would not leap into replacing anything!
No. The car has been at the Audi dealer for 9 days. They haven't done anything to make me think they're capable or willing to do a proper diagnosis. I called today for an update and was told the entire diff needs to be replaced.
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Old 01-10-2018, 01:25 PM
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Originally Posted by DrGP View Post
What would happen if you did nothing? Would the dif work without vectoring? Dealer will charge you much more to do the job than an independent mechanic.Labor rates are so much higher.
I've been driving it for several months and haven't noticed any leaking, bad sounds or problems with the performance.
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Old 01-10-2018, 01:28 PM
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Originally Posted by plat27265 View Post
Here is a thread that discussing the same fault codes that point to the B8 S4 Sport Differential failure: Sports Differential System Fault

It seems that the problem stems from a leak in one or more seals. There seems to be a Technical Service Bulletin for this issue. You can read it here: Sport Rear Differential Oil Leak - Known Issue? - Page 6
Thanks. I did see that thread. I don't believe the TSB related issue is my problem, though, as I don't see any leak - these folks are claiming unmissable huge leaks.

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Old 01-10-2018, 01:55 PM
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Originally Posted by BoxcuTTer View Post
Thanks. I did see that thread. I don't believe the TSB related issue is my problem, though, as I don't see any leak - these folks are claiming unmissable huge leaks.
I wonder what is wrong with your car's sport diff. Those things just don't give up for no reason at all. I wonder if it failed due to oil starvation. There may not be an unmissable fluid leak but it may have been a slow leak. I doubt if you have the old oil from the diff. BTW, I think there are two kinds of oil in it. One that uses Diff fluid and another that uses ATF. Did your mechanic replace both? I wonder if the oil he took out is the same amount of oil he put in or close to it. If not, that means there was indeed a very slow leak and the gears inside are toast. Otherwise, I could not think of anything else that would be the cause of this failure.

I did a search on Ebay and found this one: https://www.ebay.com/itm/AUDI-S4-S5-...FYQAA8&vxp=mtr

You can definitely have an independent Audi shop replace it if you don't want to pay dealer service shop prices.
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Old 01-10-2018, 02:15 PM
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Originally Posted by plat27265 View Post
I wonder if the oil he took out is the same amount of oil he put in or close to it. If not, that means there was indeed a very slow leak and the gears inside are toast. Otherwise, I could not think of anything else that would be the cause of this failure.

I did a search on Ebay and found this one: https://www.ebay.com/itm/AUDI-S4-S5-...FYQAA8&vxp=mtr
Thanks. Anything's possible I guess - but if the thing was starved of fluid I'm thinking I would have signs of mechanical failure by now.

Do you know the part number for that item?
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Old 01-10-2018, 02:37 PM
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Originally Posted by BoxcuTTer View Post
Thanks. Anything's possible I guess - but if the thing was starved of fluid I'm thinking I would have signs of mechanical failure by now.

Do you know the part number for that item?
0BF500043S. You quoted 0BF500043Q in your original post. The Ebay ad says it is only for a manual tranny S4. I am guessing your car has the S-tronic tranny. Am I correct? If so, then I found you the wrong part.

Last edited by plat27265; 01-10-2018 at 02:43 PM.
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