05 cooper s with 125k,6-speed automatic.
So, after 3 drains of ATF fluid (1-1.5 quarts) each time, I have no shame in saying that the transmission shifting, jerking, ....etc ha gotten at least 50% better.
The car still drives better when cold, than when warm.
Two main problems: slamming or jerking AND the feeling of it being in neutral before catching the next gear.
The jerking/slamming when the transmission changes gears is much harsher in downshifting than up-shifting.
Not sure if this is another problem, an adaptation issue, a tranny issue: It seems as if the car changes from 1st to 2nd to 3rd gears really fast at very low speed, but when I drive it say off of traffic light it changes much better.
Could not see any metal or grindings in the fluid, although I did not remove the pan.
There seems to be no ATF leaks from anywhere, so I know she wasn't starving fluid from previous owner.
I bought it knowing it has a tranny issue, took a chance, having I negotiated the price really well.
On the hwy the car drives perfect, and I mean perfect, with no issues.
Now, the fluid looks much better as it did before, and when I fill it up and I watch the fluid drains out it looks pretty good. I am sure I haven't flushed most of the fluid out yet.
How do I differentiate whether the problem is electrical, valve body, transmission, more drain-fill, re-learning procedure? Without getting screwed by the dealership as I have read in many posts.
What do you guys think the first thing I should go about the next step? Ask the dealer to do a diagnosis and tell me I need another tranny like they did to many people? Tell them to adapt it? Reset it?
How can someone diagnose the valve body? by INPA scanner? REMAX sells them for $650 and am willing to buy it if that is the issue.

Any feedback is appreciated.
The car is well worth it for me: it was never wrecked, convertible, S type, leather, heated seats, navigation, new top, everything works on it, factory hood stripes, tires with plenty of tread left, and no other issues.

 

Hello There...I am wondering if you got your issue resolved, seems that I am having a very similar issue as yours. I bought the car and actually replaced the valve body from REMAX at 99k miles. worked great. Now the car has 127k and small jerking issues on 2nd and 3rd gear, however, drives perfect when cold and the jerking does't happen all the times. it's 2006 Cooper S Convertible R52 with excellent condition and everything on it works, the top is in excellent condition. I even replaced seats with leather ones. I am thinking of changing the transmission fluid and reset the adaptation hoping this will fix it....open for any suggestions or recommendations to do and possibly fix the issue without breaking the wallet....Thank you

 

Around 30K miles seems like a good interval to change the fluid on these transmissions. The fluid should be JWS-3309 spec'd and in the proper temperature range when replacing so the level is correct. If the fluid is too cold the level will be high, and low if too hot.

Adjusting the valve body might solve the issue if changing the fluid and resetting the adaptations doesn't work.

Here's a link for Sonnax with a bunch of info on the valve body, including why and how-to adjust it to possibly correct shifting problems in the Adjusting Clutch Control Valves related tech link: https://www.sonnax.com/parts/3987-re...red-valve-body

The Tech & Install Tips button has info on resetting the adaptations.