SOLVED Transmission slipping for the S550 w221
Thread Starter
Newbie
Joined: Apr 2023
Posts: 4
Likes: 1
W221
SOLVED Transmission slipping for the S550 w221
Had my 221 for almost 6 months and recently been facing this problem where the 7g would start slipping in all gears after 15 minutes of driving and get hiccups while driving and check engine light would come on
went to several MB shops to try and find the correct diagnostics for the problem and spend 300$ just for them to check the car
first shops tried to rip me off by trying to get me to change the conductor plate which costs 1000$ for a used one
second shop opt for a trans replacement which cost 2500$
Last one tried to convince me that the torque converter is bad and needs to be replaced 1000$ for a used one
Here is what i did : Spent the hole week looking online for the symptoms for all the problems mentioned before and non came any close to my problem
So out of frustration i decided to check the trans temp all by myself because non of the shop even bothered to check, found out its almost 250f ( normal is 230f Max ), So i decided to bye a huge oil cooler "400000units" costed 100 bucks installed bye myself in my garage... and guess what!!! NO MORE SLIPPING OR HICCUPS
went to several MB shops to try and find the correct diagnostics for the problem and spend 300$ just for them to check the car
first shops tried to rip me off by trying to get me to change the conductor plate which costs 1000$ for a used one
second shop opt for a trans replacement which cost 2500$
Last one tried to convince me that the torque converter is bad and needs to be replaced 1000$ for a used one
Here is what i did : Spent the hole week looking online for the symptoms for all the problems mentioned before and non came any close to my problem
So out of frustration i decided to check the trans temp all by myself because non of the shop even bothered to check, found out its almost 250f ( normal is 230f Max ), So i decided to bye a huge oil cooler "400000units" costed 100 bucks installed bye myself in my garage... and guess what!!! NO MORE SLIPPING OR HICCUPS
MBWorld Fanatic!
Joined: Aug 2014
Posts: 5,317
Likes: 1,673
S500
the 3 points of faults are all NORMAL "designed in, age related features" on these horrible gearboxes - they are made of chocolate, cooling the trans fluid will be a temporary silly idea masking known issues
Thread Starter
Newbie
Joined: Apr 2023
Posts: 4
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W221
drove 1500 miles with the new cooler and all seems alright
MBWorld Fanatic!
Joined: Aug 2014
Posts: 5,317
Likes: 1,673
S500
the electric TC lock up clutch fails - can lead to jerky changes and or stalling selecting first especially with cold trans fluid. Its a very common Merc issue $2000 to £3000 fitted (80 to 120k miles)
the conductor plate has two tiny speed sensor electronic things that just fail - one can be replaced and re-soldered on the board, but the other isn't replaceable, whilst it fails less the whole board is accent $800 to $1200 (age or 100k)
the ISM on the outside switches off in software after x operations, and that's another $1200 (usually from the 100k mile mark)
the 6 solenoids hate the swarf in the trans fluid as the seals get damaged - its a nice feature - as each ones gauze filter blocking slows the speed the plates engage, leading to nasty changes and more clutch and metal debris - thus its a self fulfilling maintenance opportunity for the dealers
the conductor plate has two tiny speed sensor electronic things that just fail - one can be replaced and re-soldered on the board, but the other isn't replaceable, whilst it fails less the whole board is accent $800 to $1200 (age or 100k)
the ISM on the outside switches off in software after x operations, and that's another $1200 (usually from the 100k mile mark)
the 6 solenoids hate the swarf in the trans fluid as the seals get damaged - its a nice feature - as each ones gauze filter blocking slows the speed the plates engage, leading to nasty changes and more clutch and metal debris - thus its a self fulfilling maintenance opportunity for the dealers
Thread Starter
Newbie
Joined: Apr 2023
Posts: 4
Likes: 1
W221
the electric TC lock up clutch fails - can lead to jerky changes and or stalling selecting first especially with cold trans fluid. Its a very common Merc issue $2000 to £3000 fitted (80 to 120k miles)
the conductor plate has two tiny speed sensor electronic things that just fail - one can be replaced and re-soldered on the board, but the other isn't replaceable, whilst it fails less the whole board is accent $800 to $1200 (age or 100k)
the ISM on the outside switches off in software after x operations, and that's another $1200 (usually from the 100k mile mark)
the 6 solenoids hate the swarf in the trans fluid as the seals get damaged - its a nice feature - as each ones gauze filter blocking slows the speed the plates engage, leading to nasty changes and more clutch and metal debris - thus its a self fulfilling maintenance opportunity for the dealers
the conductor plate has two tiny speed sensor electronic things that just fail - one can be replaced and re-soldered on the board, but the other isn't replaceable, whilst it fails less the whole board is accent $800 to $1200 (age or 100k)
the ISM on the outside switches off in software after x operations, and that's another $1200 (usually from the 100k mile mark)
the 6 solenoids hate the swarf in the trans fluid as the seals get damaged - its a nice feature - as each ones gauze filter blocking slows the speed the plates engage, leading to nasty changes and more clutch and metal debris - thus its a self fulfilling maintenance opportunity for the dealers
i checked fluid. It was clean no shavings whatsoever, and no jerky shifts
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Joined: Aug 2014
Posts: 5,317
Likes: 1,673
S500
but the slipping / not slipping doesn't come from clean oil - or indeed its temperature
wear has worn the insides and or the pressure applying things is insufficient - diagnostic info on these will show how hard its trying to stop slipping / change gear well. Which bit is letting go and how much it has to pump up the clutches to try and compensate for wear is all in the fill rates u see with the right equipment
diagnostics is incredible on modern cars with merc and bm going way deeper than the rest
wear has worn the insides and or the pressure applying things is insufficient - diagnostic info on these will show how hard its trying to stop slipping / change gear well. Which bit is letting go and how much it has to pump up the clutches to try and compensate for wear is all in the fill rates u see with the right equipment
diagnostics is incredible on modern cars with merc and bm going way deeper than the rest
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