W205 e-LSD - wheel slip during low speed maneuvering
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Joined: Apr 2013
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From: Culver City, CA
F10 M5 Comp, 2012 Ford Raptor
W205 e-LSD - wheel slip during low speed maneuvering
Hi all - I am researching the W205 and noticed the mechanical LSD was dropped in 2018 and all newer models have the e-LSD. The driveway to my house has an apron where the car dips before going up the driveway, which causes one of the rear wheels to lift off the ground a bit as the threshold is crossed. In my W204 C63 with the mechanical LSD, this is not a problem. However, when I owned an Alfa Romeo Giulia QV with an e-LSD, the wheel off the ground would spin and the car would "beach" itself, because the speed was too low to send a slip signal to the traction control system and ultimately send power to the wheel that wasn't spinning. This was an issue when turning into parking lots as well since the turn had to be taken slowly to prevent scraping, and it was cumbersome to deal with as a daily driver. Is this an issue with the W205's e-LSD?
Last edited by cloverfield; Jun 22, 2021 at 10:46 AM. Reason: typo
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Joined: Nov 2018
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From: San Francisco Bay Area
2019 C63CS
Based on what I found, the Alfa's rear differential is a torque vectoring differential and not a locking differential. It's specifically designed to overdrive the outer wheel during cornering via two clutches and an overdrive gearset, one for each wheel. I believe they use a ZF unit. I had such a differential in my 2013 Audi RS5. These differentials can't lock, so they can't necessarily send all the torque to a single wheel at low speeds w/o using the brakes to slow down the spinning wheel. In my RS5 a situation like yours was not an issue with quattro as the front wheels simply pulled the car over the obstacle.
Starting with MY2019 both the C63 and C63S have an electronic locking differential. Prior to that the C63 non-S had a mechanical LSD. Both are locking differentials, though. The e-diff can lock a 100% at any speed, so your situation is generally not an issue. I've driven over such driveways and I've also parked with one wheel in the sand. The wheel might spin a bit initially, but it quickly locks the differential to send torque to the wheel with traction. The C63's locking differential also torque vectors, but it does it by varying the locking ratio and with the help of the brakes if necessary. It only has one clutch to fully lock both half shafts together.
Starting with MY2019 both the C63 and C63S have an electronic locking differential. Prior to that the C63 non-S had a mechanical LSD. Both are locking differentials, though. The e-diff can lock a 100% at any speed, so your situation is generally not an issue. I've driven over such driveways and I've also parked with one wheel in the sand. The wheel might spin a bit initially, but it quickly locks the differential to send torque to the wheel with traction. The C63's locking differential also torque vectors, but it does it by varying the locking ratio and with the help of the brakes if necessary. It only has one clutch to fully lock both half shafts together.
Last edited by superswiss; Jun 22, 2021 at 11:23 AM.
Thread Starter
Member
Joined: Apr 2013
Posts: 98
Likes: 7
From: Culver City, CA
F10 M5 Comp, 2012 Ford Raptor
Excellent info - thank you. I never noticed it in my B8.5 RS 5, likely because of exactly what you mentioned. Great to know the e-LSD in the C63 is sophisticated enough to deal with these random real-world situations that cause headaches for the ZF unit in the QV.
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