The size difference from the 6L90e is 300mm vs 8L90e 258mm, which is 32mm total. No where near half the size. The biggest issue is the tuning, which is optimized for fuel economy. There are a lot of users on various messages boards that have done the tuning to the TCM to improve shifting that has also helped with the shuddering issue. The problem is the cost to do this, especially on the 17+ models with the newer TCM that has to be unlocked before it can be tuned. It can be upwards of $2000+ for tuning on the newer vehicles because GM has started locking down all the PCMs and TCMs. Not to mention it will void your warranty if you still happen to have one.