Hi Gerd,
What is confusing is that the transmission box alone is specified to take 6 US pints or 2.8 liters with the remaining to 1.5 US pints or 0.8 liters to satisfy the OD. Your level pf 5.5 US pints is less then what is called for for just the transmission. This gives me the impression that your approach to filling and exercising the trans and OD is either not as effective as it would seem or there is something, internally, blocking the flow of fluid. Since you have indicated having the OD activate and deactivate, I am wondering if, during assembly, used a lubrication grease that has blocked some passages and not as yet opened to flow or, as some, filled the OD prior to final assembly and forgotten to include in the calculation.
As it seems to appear from your initial question and approach, I do not feel it probable that you forgot the additional fill, however, I could not rule this out if it were MY experience (not as sharp as when younger). If the transmission/OD has been installed, I would exercise the transmission/OD in a nearby careful run and drain fluids from the transmission/OD, being careful not to contaminate for reuse. I then would go through the process for a refill and determine if there is a difference. If, and only if, not, I would have no choice in settling my mind but to pull the unit and investigate the internals of the trans/OD.
Yes, I don't think trans/OD removal will be required but it is an obvious option,
Ray(64BJ8P1)