Key things I have found when working on these transmissions are; 1) If a service has not been done in more than 50k miles, I generally do multiple drain and fills, usually 5-6 over a 1 month time frame. I just drain pan and refill. On the 5-6 drain and fill I add either a can of TransTune by SeaFoam or 20 oz of HotShot Secret Transmission Stiction Eliminator and run it for at least 500 miles. I then do one more drain and fill. Run it for 500 plus miles and then look at doing a full flush by the Gibons meathod or similar. The goal is to get all of the junk out and end up with solid clean fluid. In the case of my S60 I am currently at the point of getting ready to do a full flush of the system. I have been inside and replaced all of the 8 solenoids and the B4 servo. I have done the relearning reset 4 times do to the steps I have taken. In the long run I have had to replace the top and bottom torque mounts. I went with poly and have noticed much better shifting. I have also noticed in the last few days that I will need new motor mounts soon.
Use only 3309 fluid. Always fill via the dipstick tube. NEVER REMOVE THE 27 mm Bolt. Be careful removing and installing the pan. Look at all mounts. Check for vacuum leaks. I generally try to underfill my trans by a cup or so of fluid so I can get it good and warm and check the fluid level and top off as needed. Easier to top off than to drain out of a hot motor. So, just be careful and look at as many write ups as you can find until you have the process down in your mind. If you are mechanical then you should be able to get this done in a day. If you are worried about anything, add a day. Make sure you have every possible part handy when you start because the part that you don’t want to break, will and it will do it at 10pm on a Sunday when there is no chance of getting a replacement.
When I do this the way I do, I end up using about 2 1/2 cases of trans fluid. I end up with ruby red fluid and I have now fixed 3 geartronic transmission with different issues that the dealer and trans shops have said were toast and needed to be replaced. The first 2 are still going strong after more than 30k miles since work. Those 2 are due for fluid flushes soon. So far the worst one has been my S60 and after new solenoids and B4 servo with all of the trans fluid and additives I have used, I am into it about $600 and it shifts like new now. The biggest thing to figure out was that the previous lot that had it removed the 27 mm bolt to fill it with fluid. I bought it with no third gear. Thanks to Phixion and others that helped me talk out the issues and finally resolve the issue. It came down to 2 sets of hands, a flashlight, a length of coat hanger, removing the B4 servo and cover, and a little luck. I was able to grab the end of the B4 band and pull it around and get the 27 mm bolt back in and secured. Fired her up and had third gear. Total it took me about 45 mins to fix it. Was getting quotes of $4,500 plus to fix.