Questions? We've got answers.
We have confirmed we can do this retrofit into the following 0BC rear differential casings. Codes:
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JKP - early B8 A4 6MT
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JKQ - early B8 S4 6MT
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JKS - B8 S4 DSG
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KCC - C7 A6 Auto
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KLL - B8 Q5
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KLM - B8.5 RS5
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KRR - late B8 A4 Auto
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LWV - C7 A6 TDI
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MFS - late B8 A4 6MT
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MFT - late B8 S4 6MT
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MNB - C7 S6/S7
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NPR - C7 A6/A7 Auto, C7 RS6/RS7, D4 A8/S8, B8 Q5/SQ5
If you have a Sport Diff with any of the following codes, you can convert by switching as follows:
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MKY —> MFT - B8 S4 6MT
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MKX —> JKS - B8 S4 DSG
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MKU —> MNB - C7 S6/S7
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MKV —> NPR - C7 RS6/RS7, D4 A8/S8
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MKW —> KLM - B8.5 RS5
Please note if you are switching from Sport Diff you will need to source different rear axles. See SPORT DIFF CONVERSION section. You will also need to code out the Sport Diff using VCDS. On the C7/D4, you will need to code it out PRIOR to unplugging the Sport Diff. On the C7/D4, it is impossible to clear codes permanently with the Sport Diff unplugged.
BENEFITS COMPARED TO THE OEM REGULAR DIFF
The “regular diff” is just a standard open differential. That means as soon as one wheel loses traction, all torque is delivered to it. It makes for crappy handling characteristics in low traction situations (ice and snow), off the line, and in corners. With the LSD:
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Acceleration - you’ll get off the line faster with less wheel spin.
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Cornering - you’ll be able to put much more power down in the corners, since torque is split to match available traction. No more spinning the inside rear.
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Drivability - the LSD does not create any additional NVH. It is purely gear-based. It creates no noise or strange handling characteristics. It’s a 100% OEM+ kind of mod. It just does everything better.
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Strength - The LSD’s helical construction is much stronger than the 2-pinion spider gear open diff. You won’t break it.
BENEFITS OVER THE SPORT DIFF
The Sport Diff is a great differential for road course racing, autocrossing, or when you’re pushing to the limits in a corner. It has a lot of weaknesses though. The first is that at it’s heart it’s actually an open differential, just like the regular diff. The Sport Diff is a “torque override differential” which means it has a special clutch-pack-driven override gear that can apply more torque to the outer axle in a turn. Because of this, the differential itself must be open by design, as an LSD would fight the torque override gear. That means anytime you’re in a low traction scenario or lift a wheel in a turn, the differential becomes open. In our autocross car, we always wear out the insides of the rear tires first, and on a particularly violent course, we actually find the inside of the rear tires smoking!! That’s the typical sign of an open diff.
It’s other great weakness is in strength and durability. There are several weak points in the design. The casing is weak at the attachment points and has been known to break free from the car on launches and 1-2 shifts, damaging other components. The spider gears in the heart of the differential are weak and can break. Clutch packs can wear out over time, limiting the effectiveness of the torque override gears. Not to mention all the other components (pump, sensors, control module) that can break or develop faults.
Broken spider gears from a Sport diff. All torque is sent through these 2 gears.
The WaveTrac LSD is a helical differential. Torque is transmitted in the LSD by 5 pairs of helical gears.
Regular diff on the left. Sport diff on the right. The Sport diff is mounted by 2 bolts on the outer housings. The mounting points are prone to failure. The regular diff uses an adapter plate with reinforced subframe mounting points, and bolts into the differential casing at 4 integral mounting points.
4 casing mounting points of the regular diff. The upper 2 points are particularly robust. The lower 2, while not as strongly integrated into the casing, are a bonus over the sport diff.
The 2 halves of the casing are held together by 10 bolts. The casing mounting points are well-integrated into the back half of the casing.
All in all, the Sport Diff just isn’t very robust. It’s great for a couple of specific things, but that’s about it. Plus it’s really heavy.
Sport diff weighing in at 93 lbs dry.
Regular diff weighing in at 53 lbs dry.
So, compared to the Sport Diff:
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Strength - This is where the LSD truly shines compared to the Sport Diff. The casing and gears of the Sport Diff are weak and prone to failure. The LSD is much more robust.
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Acceleration - the LSD is able to keep the wheels locked together, even under wheel spin conditions. You’ll have more traction off the line.
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Weight - the LSD is over 35 lbs lighter than the Sport Diff. In the 1/4 mile, 100 lbs is conservatively worth 0.1s, so this weight savings alone is worth in the neighborhood of 4-5 hundreths based on weight alone.
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Drivability - the LSD does not create any additional NVH. It is purely gear-based. It creates no noise or strange handling characteristics. It’s a 100% OEM+ kind of mod.
