Thinking about buying a 2013 or 2015 RS5...

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01-09-2019, 05:04 AM

#11

superswiss

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Quote:

Originally Posted by J. Patterson

Good analysis SuperSwiss. I too looked up the relative final drive gear ratios and engine torque outputs. Peak torque loads at the he axle appear to be approx 17% higher on the RS with the input shaft and pinion rotating about 19% faster. Whether this justifies a 20000 mile service interval on the RS vs a life of the vehicle interval on the S is a job for the engineers. My instincts given the lower overal transmission ratios of a manual trans car like mine make me lean toward having a service done at my next engine service. (35000 mi). My 3,0 has not been tuned ( yet) but the temptation is real. I usually do my own services. I’ve serviced Haldex final drives on TTs many times but this will be new to me.
Has anybody done their own sport diff? I’ll be looking up a diy guide.

Manufacturers add in a lot of headroom into their designs to ensure longevity. The SD is an expensive piece of equipment and having it fail widely would not be good for Audi. Audi Sport obviously found it necessary to do the extra maintenance. There is also a correlation between owners driving higher output cars harder than lower output cars and it's more likely that they are taken to the track. While the diff might be fine w/o this extra maintenance for somebody who doesn't drive the car hard, Audi Sport obviously designed the car to handle more than just grocery shopping. Generally somebody who buys a high performance version of a car has certain plans. It's a very small group of customers around 1%, so these are not exactly mainstream cars. The S is positioned as more like an A5 with a sporty attitude. Extra diff maintenance is not unusual at the top echelon of performance cars. The C63 S for example requires the first diff fluid change at 2000 miles. Don't know about the M3/4's M Differential, but I'm guessing it has similar requirements.

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01-09-2019, 06:59 AM

#12

Ape Factory

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Quote:

Originally Posted by J. Patterson

Servicing the rear differential is actually super easy. I have a writeup over on Audizine. You can use Motul Gear 300 on the mechanical MTF side and the only offering for the ATF side is Audi's fluid which is about $45 for a liter. You'll need one of each. Not sure if the S uses the same ATF side fluid as the RS. Best to check.
https://www.audizine.com/forum/showt...r-differential)