As I have built a few transmissions along the way a have a few questions.
Can someone tell me the purpose of dropping the valve body and replacing all these seals? I would assume that this is stated in the BMW procedure somewhere? These transmissions are build in clean rooms. Likely you could just introduce debris into the non-filter side of the transmission. Do the seals degrade? If so is there data to suggest this? The XM having a ZF 6HP26S, a heavy duty version of a 6HP with a metal pan
ZF's procedure is here. why go beyond?: