Hard downshift on deceleration at lower speeds
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Joined: Aug 2017
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w212
Hard downshift on deceleration at lower speeds
Sup guys. I've owned and loved my W212 for about a decade, unfortunately, she has started acting up a bit. At lower speeds (under 20 mph) I can feel a delayed or rough shift when downshifting from either 3rd to 2nd or 2nd to 1st (not sure which one, I have further diagnostics to run) Needless to say I am anxious about it, she's been my loyal steed for a long time and I want to fix it asap. Car has about 77k miles on it, have never serviced the transmission. Indy shop said a fluid and filter might or might not help, transmission service at the indy shop is $600. Dealership said to bring it in for diagnostic ($250), they will run the scanner to see if any codes come up. I read about a transmission reflash on w212's? Just looking for ideas or suggestions before I spend the cash. Any input is welcome.
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From: Jakarta-Indonesia
2014 - W212.065 - E400 ( M276.820, 3 liter Turbo) RWD not Hybrid
Sup guys. I've owned and loved my W212 for about a decade, unfortunately, she has started acting up a bit. At lower speeds (under 20 mph) I can feel a delayed or rough shift when downshifting from either 3rd to 2nd or 2nd to 1st (not sure which one, I have further diagnostics to run) Needless to say I am anxious about it, she's been my loyal steed for a long time and I want to fix it asap.Car has about 77k miles on it, have never serviced the transmission. Indy shop said a fluid and filter might or might not help, transmission service at the indy shop is $600. Dealership said to bring it in for diagnostic ($250), they will run the scanner to see if any codes come up. I read about a transmission reflash on w212's? Just looking for ideas or suggestions before I spend the cash. Any input is welcome.
I though you love ur car ?
The annswer lies with the tranny fluid + filter replacement....but you may need to do it more than once.
Good luck.......
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Don't recommend flushing right? Introduces air?
Out Of Control!!
Joined: Apr 2019
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From: Silicon Valley
W212 MY'14 M276-3.5NA @75kMi
Maintenance Or Repairs !!
The tranny may need to clean valve body screens if fresh ATF can not restore pressure control.
When you're all done dealing with tranny, everything else needs scheduled maintenance parts:
When you're all done dealing with tranny, everything else needs scheduled maintenance parts:
- engine 5k oil/ignition/fuel
- differential gear oil
- brakes rotors/pads/steel lines
- suspensions/steering
- electricals *.*
Last edited by CaliBenzDriver; Feb 14, 2025 at 07:20 PM.
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2014 E350 4Matic
"they will run the scanner to see if any codes come up"
You can get an Openport 2.0 clone (AliExpress clone) + Xentry for under $30. PM me if you need help with the Xentry part. This could save you the $250 for them to attach their scanner and tell you it finds nothing.
You can get an Openport 2.0 clone (AliExpress clone) + Xentry for under $30. PM me if you need help with the Xentry part. This could save you the $250 for them to attach their scanner and tell you it finds nothing.
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2019 AMG GT
Just went through something similar. Hard and missed shifts. It puzzled me since I had an independent do a recent transmission filter and fluid change on my 2012 with 49k miles. I finally gave up and took it in to the dealer to diagnose and they told me it was low 3 quarts. They added the fluid and had to "Re-adapt" the shift points (they get messed up when pressures fluctuate) which has to be done after the temperature reaches the proper operating range. It now shifts as smooth as butter. BTW during my research, I found out that there are two solenoids above the valve body that accumulate (magnetically) metal shavings that may also mess up the shift points but that was not the case for mine. My recommendation is that unless your independent is thoroughly experienced with this process to include the re-adaptation of the shift points, then you should take it to the dealer. After an exhaustive learning process I am glad I took it in. Hope this helps and best of luck.
Oh BTW, there were no codes during the erratic shifts.
Oh BTW, there were no codes during the erratic shifts.
Last edited by HHS550; Feb 15, 2025 at 02:39 AM.
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Just went through something similar. Hard and missed shifts. It puzzled me since I had an independent do a recent transmission filter and fluid change on my 2012 with 49k miles. I finally gave up and took it in to the dealer to diagnose and they told me it was low 3 quarts. They added the fluid and had to "Re-adapt" the shift points (they get messed up when pressures fluctuate) which has to be done after the temperature reaches the proper operating range. It now shifts as smooth as butter. BTW during my research, I found out that there are two solenoids above the valve body that accumulate (magnetically) metal shavings that may also mess up the shift points but that was not the case for mine. My recommendation is that unless your independent is thoroughly experienced with this process to include the re-adaptation of the shift points, then you should take it to the dealer. After an exhaustive learning process I am glad I took it in. Hope this helps and best of luck.
Oh BTW, there were no codes during the erratic shifts.
Oh BTW, there were no codes during the erratic shifts.
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From: Jakarta-Indonesia
2014 - W212.065 - E400 ( M276.820, 3 liter Turbo) RWD not Hybrid
If torque converter has the drain plug, it is good enough for near 100% drain.
If TQ has no drain plug, the "oil-push" adapter would be good to use.
This adapter fits at the filter port and you can then push new oil into it and TC will get the new oil.
I would not call this a flush per se.
One of this below is the adapter I speak of....
Air trapped in oil will go away when tranny oil pumps starts running, no worry...as long as fluid level is proper
If TQ has no drain plug, the "oil-push" adapter would be good to use.
This adapter fits at the filter port and you can then push new oil into it and TC will get the new oil.
I would not call this a flush per se.
One of this below is the adapter I speak of....
Air trapped in oil will go away when tranny oil pumps starts running, no worry...as long as fluid level is proper
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MBWorld God!
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If torque converter has the drain plug, it is good enough for near 100% drain.
If TQ has no drain plug, the "oil-push" adapter would be good to use.
This adapter fits at the filter port and you can then push new oil into it and TC will get the new oil.
I would not call this a flush per se.
One of this below is the adapter I speak of....
Air trapped in oil will go away when tranny oil pumps starts running, no worry...as long as fluid level is proper
If TQ has no drain plug, the "oil-push" adapter would be good to use.
This adapter fits at the filter port and you can then push new oil into it and TC will get the new oil.
I would not call this a flush per se.
One of this below is the adapter I speak of....
Air trapped in oil will go away when tranny oil pumps starts running, no worry...as long as fluid level is proper
Joined: Nov 2016
Posts: 7,847
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From: Maryland
2015 SL400 (M276 Turbo), 2014 C350 Sport (M276 NA), 2004 SL500 (M113), 2004 Audi TT225 (BEA)
Thread Starter
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Joined: Aug 2017
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w212
Have an update in case anyone is interested. Took it to Mercedes benz of Chicago, tech said he believed it was most likely fluid and filter (him, his dad and his mom all own w212s and in the video inspection sounded like he knew what he was talking about). I ok'd it and 3 days and $1,200 later, I felt the dreaded hard shift on my way home, I feel it particularly from 4th to 5th at slower speeds and also from 4th to 3rd at slower speeds. Kind of disappointed to be honest, I was trying to get it right the first time, hence my taking it to the dealership. Going to give service a call tomorrow and see what they say. The service guy said that the tech test drove it after the fluid swap, I'm not so sure. My question is, if they needed to service the valves, would they charge me again for the fluid and filter? Before the fluid swap was done, the advisor did mention how sometimes valves need adjustment and said it's about $2000. I would have honestly paid that from the beginning in order to go through whatever im gonna go through. Don't they have special equipment to diagnose things like this? Mildly annoyed...
Out Of Control!!
Joined: Apr 2019
Posts: 12,272
Likes: 6,918
From: Silicon Valley
W212 MY'14 M276-3.5NA @75kMi
Have an update in case anyone is interested. Took it to Mercedes benz of Chicago, tech said he believed it was most likely fluid and filter (him, his dad and his mom all own w212s and in the video inspection sounded like he knew what he was talking about). I ok'd it and 3 days and $1,200 later, I felt the dreaded hard shift on my way home, I feel it particularly from 4th to 5th at slower speeds and also from 4th to 3rd at slower speeds. Kind of disappointed to be honest, I was trying to get it right the first time, hence my taking it to the dealership. Going to give service a call tomorrow and see what they say. The service guy said that the tech test drove it after the fluid swap, I'm not so sure. My question is, if they needed to service the valves, would they charge me again for the fluid and filter? Before the fluid swap was done, the advisor did mention how sometimes valves need adjustment and said it's about $2000. I would have honestly paid that from the beginning in order to go through whatever im gonna go through. Don't they have special equipment to diagnose things like this? Mildly annoyed...
Every service is extra cost.
Personally I would discourage wasting $2000 in adaptations. Tranny dies that all by itself very well when possible.
Meaning you can spend $2k now and still have jacked up shifts next month after tranny has relearned sloppy shifts.
Personally I think this has everything to do with poor stock throttle control that prevent TCU from learning shift points.
TCU shifts up/down at the wrong Rpm and CAN-C adds delay on top of that.
Realize that TCU is forced to use maximum pressure to slam clutch packs during these shifts.
Never mind adaptations in that context. Now that ATF is clean with less contaminants, drive around normally to let ECU/TCU work together. Don't overheat neither engine nor tranny: this f's up much needed viscosity.
Last edited by CaliBenzDriver; Mar 7, 2025 at 01:49 AM.
MBWorld God!
Joined: Dec 2019
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Have an update in case anyone is interested. Took it to Mercedes benz of Chicago, tech said he believed it was most likely fluid and filter (him, his dad and his mom all own w212s and in the video inspection sounded like he knew what he was talking about). I ok'd it and 3 days and $1,200 later, I felt the dreaded hard shift on my way home, I feel it particularly from 4th to 5th at slower speeds and also from 4th to 3rd at slower speeds. Kind of disappointed to be honest, I was trying to get it right the first time, hence my taking it to the dealership. Going to give service a call tomorrow and see what they say. The service guy said that the tech test drove it after the fluid swap, I'm not so sure. My question is, if they needed to service the valves, would they charge me again for the fluid and filter? Before the fluid swap was done, the advisor did mention how sometimes valves need adjustment and said it's about $2000. I would have honestly paid that from the beginning in order to go through whatever im gonna go through. Don't they have special equipment to diagnose things like this? Mildly annoyed...
MBWorld God!
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Youve just had a good tranny ATF service at dealer but shifts are still not great.
Every service is extra cost.
Personally I would discourage wasting $2000 in adaptations. Tranny dies that all by itself very well when possible.
Meaning you can spend $2k now and still have jacked up shifts next month after tranny has relearned sloppy shifts.
Personally I think this has everything to do with poor stock throttle control that prevent TCU from learning shift points.
TCU shifts up/down at the wrong Rpm and CAN-C adds delay on top of that.
Realize that TCU is forced to use maximum pressure to slam clutch packs during these shifts.
Never mind adaptations in that context. Now that ATF is clean with less contaminants, drive around normally to let ECU/TCU work together. Don't overheat neither engine nor tranny: this f's up much needed viscosity.
Every service is extra cost.
Personally I would discourage wasting $2000 in adaptations. Tranny dies that all by itself very well when possible.
Meaning you can spend $2k now and still have jacked up shifts next month after tranny has relearned sloppy shifts.
Personally I think this has everything to do with poor stock throttle control that prevent TCU from learning shift points.
TCU shifts up/down at the wrong Rpm and CAN-C adds delay on top of that.
Realize that TCU is forced to use maximum pressure to slam clutch packs during these shifts.
Never mind adaptations in that context. Now that ATF is clean with less contaminants, drive around normally to let ECU/TCU work together. Don't overheat neither engine nor tranny: this f's up much needed viscosity.
Thread Starter
Junior Member
Joined: Aug 2017
Posts: 70
Likes: 10
w212
Youve just had a good tranny ATF service at dealer but shifts are still not great.
Every service is extra cost.
Personally I would discourage wasting $2000 in adaptations. Tranny dies that all by itself very well when possible.
Meaning you can spend $2k now and still have jacked up shifts next month after tranny has relearned sloppy shifts.
Personally I think this has everything to do with poor stock throttle control that prevent TCU from learning shift points.
TCU shifts up/down at the wrong Rpm and CAN-C adds delay on top of that.
Realize that TCU is forced to use maximum pressure to slam clutch packs during these shifts.
Never mind adaptations in that context. Now that ATF is clean with less contaminants, drive around normally to let ECU/TCU work together. Don't overheat neither engine nor tranny: this f's up much needed viscosity.
Every service is extra cost.
Personally I would discourage wasting $2000 in adaptations. Tranny dies that all by itself very well when possible.
Meaning you can spend $2k now and still have jacked up shifts next month after tranny has relearned sloppy shifts.
Personally I think this has everything to do with poor stock throttle control that prevent TCU from learning shift points.
TCU shifts up/down at the wrong Rpm and CAN-C adds delay on top of that.
Realize that TCU is forced to use maximum pressure to slam clutch packs during these shifts.
Never mind adaptations in that context. Now that ATF is clean with less contaminants, drive around normally to let ECU/TCU work together. Don't overheat neither engine nor tranny: this f's up much needed viscosity.
Will do, I did notice that with when accelerating and say 50% throttle or more, it shifts smoothly. I was hoping that the new oil would help the hard shifts "work themselves out". Will report back.
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From: Connecticut
2015 E 350 Wagon
For what it's worth, my 2015 S212 has a mild hard shift from 5-4 when decelerating at slow speeds, like to a stop light. 110k miles, just did transmission drain/fill and filter.
I took it to two different reputable independent shops recently, and they weren't any help at all. After checking for codes and taking it for a drive, they just said they didn't notice it.
My local dealership is a $450 standard diagnostic fee. So I'm currently just monitoring the issue to see if it gets any worse at this point. $450 is just a huge hit to take after spending $150 each on those independent shops.
I'm looking forward to hearing how things go for you. I'll let you know if I find anything out myself.
I took it to two different reputable independent shops recently, and they weren't any help at all. After checking for codes and taking it for a drive, they just said they didn't notice it.
My local dealership is a $450 standard diagnostic fee. So I'm currently just monitoring the issue to see if it gets any worse at this point. $450 is just a huge hit to take after spending $150 each on those independent shops.
I'm looking forward to hearing how things go for you. I'll let you know if I find anything out myself.
MBWorld God!
Joined: Dec 2019
Posts: 33,397
Likes: 6,629
For what it's worth, my 2015 S212 has a mild hard shift from 5-4 when decelerating at slow speeds, like to a stop light. 110k miles, just did transmission drain/fill and filter.
I took it to two different reputable independent shops recently, and they weren't any help at all. After checking for codes and taking it for a drive, they just said they didn't notice it.
My local dealership is a $450 standard diagnostic fee. So I'm currently just monitoring the issue to see if it gets any worse at this point. $450 is just a huge hit to take after spending $150 each on those independent shops.
I'm looking forward to hearing how things go for you. I'll let you know if I find anything out myself.
I took it to two different reputable independent shops recently, and they weren't any help at all. After checking for codes and taking it for a drive, they just said they didn't notice it.
My local dealership is a $450 standard diagnostic fee. So I'm currently just monitoring the issue to see if it gets any worse at this point. $450 is just a huge hit to take after spending $150 each on those independent shops.
I'm looking forward to hearing how things go for you. I'll let you know if I find anything out myself.
Junior Member
Joined: Jan 2025
Posts: 20
Likes: 13
From: Connecticut
2015 E 350 Wagon
Out Of Control!!
Joined: Apr 2019
Posts: 12,272
Likes: 6,918
From: Silicon Valley
W212 MY'14 M276-3.5NA @75kMi
For what it's worth, my 2015 S212 has a mild hard shift from 5-4 when decelerating at slow speeds, like to a stop light. 110k miles, just did transmission drain/fill and filter.
I took it to two different reputable independent shops recently, and they weren't any help at all. After checking for codes and taking it for a drive, they just said they didn't notice it.
My local dealership is a $450 standard diagnostic fee. So I'm currently just monitoring the issue to see if it gets any worse at this point. $450 is just a huge hit to take after spending $150 each on those independent shops.
I'm looking forward to hearing how things go for you. I'll let you know if I find anything out myself.
I took it to two different reputable independent shops recently, and they weren't any help at all. After checking for codes and taking it for a drive, they just said they didn't notice it.
My local dealership is a $450 standard diagnostic fee. So I'm currently just monitoring the issue to see if it gets any worse at this point. $450 is just a huge hit to take after spending $150 each on those independent shops.
I'm looking forward to hearing how things go for you. I'll let you know if I find anything out myself.
--1-- Shift adaptations relearning
or
--2-- Conductor plate swap
The diagnosis can almost be mileage based unless tranny has suffered abuse.
Last edited by CaliBenzDriver; Mar 7, 2025 at 07:29 PM.
Joined: Nov 2016
Posts: 7,847
Likes: 3,499
From: Maryland
2015 SL400 (M276 Turbo), 2014 C350 Sport (M276 NA), 2004 SL500 (M113), 2004 Audi TT225 (BEA)
Honestly, drive it around for a while. What mode do you normally drive in? If I drive the car in Sport or Agility/Sport+ timidly (i.e., the wife is in the car), my SL will downshift a little harder than I like as I slow down. I just did the CaliBenzDriver Chassis Reset earlier this week and I believe the tranny is relearning all over again. The thing is, these shift characteristics come a go randomly. You may want to try different transmission modes and see if that makes a difference.
