The 09G
So the 09G is a problematic transmission, as I mentioned in a previous thread. I have rebuilt a few of these units and internally they don't have many issues. Unfortunately, every person you dealt with is either making claims for the sole purpose of getting a sale or they are simply ignorant. I currently am working with a 09G with a 2-3 slide bump, which is intermittent. The previous owner had the dealer replace the VB because of an occassional 1-2 slide bang, which it did fix. One downfall with this unit, whether it is a VW design flaw or an Aisin-Warner design flaw (the firm that actually designed/built the transmission, yes, it is Japenese!) is the adaptive shifting system. The dealer has to force the transmission to re-learn the driving habits of the driver and this can take quite awhile as it is always modifying it's shift procedure to some set parameters. Many times the shifting will be erratic before it gets better. The long story here is 99% of the problems with the 09G is electrical (software) or valve body.
Addressing your experiences, the first shop you went to seemed to approach the problem correctly as wear and tear can be seen by inspecting the pan. Bushing wear, clutch material delamination, or just plain metal on metal wear can easily be seen here. However, the mechanic lost me when he claimed that there was nothing indicative of a valve body issue. Valve body issues are primarily valve to bore wear concerns where fluid is leaking from one side of a valve spool to another side, which may cause a plethora of issues, some noticeable and some not. The 09G uses linear valves attached to the solenoids, which have issues in terms of cross leaks or binding in the bore, causing the valve to hang up. This may be the main cause of the slide-bangs and slide-bumps but I have not seen any reports of such. In terms of the added additive, it all depends on what that additve was and what it does to the fluid. Some additives have a friction modifier which adds "teeth" to the friction material. Whether it accomplishes this by interacting with the clutch material or increasing the coefficient of friction of the transmission fluid, I do not know. This may make shifts seem to bang more as the clutches are slipping less during apply. Also, an oil cooler issue would not cause any of your mentioned symptoms, but it may have caused damage that then led to your concerns, not likely, however.
The dealer you took it to seems like your usual dealer, spitting out the same old responses and excuses rather than just saying they didn't have an answer. This transmission is not delicate. The transmission fluid is as important in this unit as it is in say, a new Camaro. Just because it is a foreign doesn't make it fragile. The transmission fluid does need to contain the proper additives in which the transmission was designed around. There are many manufacturers of fluid and they may or may not have one that meets the OEM specs for this model. Just check that the fluid in question does meet the specs asked for in the owners manual or bottle from the dealer. If the wrong fluid was installed you will usually notice other concerns such as slipping, softer shifts or harder shifts. What you probably noticed with the change in shift characteristics after the dealer visit is the adaptive shift program. They would have done a re-learn and this often fixes some of the problems related to software. I don't feel that removing the residual transmission fluid and additive from previously is going to fix anything, but it also cannot hurt.
One thing to mention about the VB is that there are companies working to fix these problems. Both Sonnax and VB Express offer upgrade parts or completely rebuilt units. The latter installs all of the Sonnax upgrades and cleans/replaces the solenoids and then tests the VB's on a flow bench to verify that there are no crossleaks or stuck valves. Look them up, but they will definitely still be expensive, but they are much, much better than the new units from VW. To the best of my knowledge, you will need to bring the car to the dealer after the VB install/rebuild to have them initiate the adaptive shift re-learn. Good luck!
So the 09G is a problematic transmission, as I mentioned in a previous thread. I have rebuilt a few of these units and internally they don't have many issues. Unfortunately, every person you dealt with is either making claims for the sole purpose of getting a sale or they are simply ignorant. I currently am working with a 09G with a 2-3 slide bump, which is intermittent. The previous owner had the dealer replace the VB because of an occassional 1-2 slide bang, which it did fix. One downfall with this unit, whether it is a VW design flaw or an Aisin-Warner design flaw (the firm that actually designed/built the transmission, yes, it is Japenese!) is the adaptive shifting system. The dealer has to force the transmission to re-learn the driving habits of the driver and this can take quite awhile as it is always modifying it's shift procedure to some set parameters. Many times the shifting will be erratic before it gets better. The long story here is 99% of the problems with the 09G is electrical (software) or valve body.
Addressing your experiences, the first shop you went to seemed to approach the problem correctly as wear and tear can be seen by inspecting the pan. Bushing wear, clutch material delamination, or just plain metal on metal wear can easily be seen here. However, the mechanic lost me when he claimed that there was nothing indicative of a valve body issue. Valve body issues are primarily valve to bore wear concerns where fluid is leaking from one side of a valve spool to another side, which may cause a plethora of issues, some noticeable and some not. The 09G uses linear valves attached to the solenoids, which have issues in terms of cross leaks or binding in the bore, causing the valve to hang up. This may be the main cause of the slide-bangs and slide-bumps but I have not seen any reports of such. In terms of the added additive, it all depends on what that additve was and what it does to the fluid. Some additives have a friction modifier which adds "teeth" to the friction material. Whether it accomplishes this by interacting with the clutch material or increasing the coefficient of friction of the transmission fluid, I do not know. This may make shifts seem to bang more as the clutches are slipping less during apply. Also, an oil cooler issue would not cause any of your mentioned symptoms, but it may have caused damage that then led to your concerns, not likely, however.
The dealer you took it to seems like your usual dealer, spitting out the same old responses and excuses rather than just saying they didn't have an answer. This transmission is not delicate. The transmission fluid is as important in this unit as it is in say, a new Camaro. Just because it is a foreign doesn't make it fragile. The transmission fluid does need to contain the proper additives in which the transmission was designed around. There are many manufacturers of fluid and they may or may not have one that meets the OEM specs for this model. Just check that the fluid in question does meet the specs asked for in the owners manual or bottle from the dealer. If the wrong fluid was installed you will usually notice other concerns such as slipping, softer shifts or harder shifts. What you probably noticed with the change in shift characteristics after the dealer visit is the adaptive shift program. They would have done a re-learn and this often fixes some of the problems related to software. I don't feel that removing the residual transmission fluid and additive from previously is going to fix anything, but it also cannot hurt.
One thing to mention about the VB is that there are companies working to fix these problems. Both Sonnax and VB Express offer upgrade parts or completely rebuilt units. The latter installs all of the Sonnax upgrades and cleans/replaces the solenoids and then tests the VB's on a flow bench to verify that there are no crossleaks or stuck valves. Look them up, but they will definitely still be expensive, but they are much, much better than the new units from VW. To the best of my knowledge, you will need to bring the car to the dealer after the VB install/rebuild to have them initiate the adaptive shift re-learn. Good luck!