Query re Zf partial flush

[Jpdv]

Hi all,
A quick question around flushing the transmission, using Robbie's guide. Given the value of the ZF Box, I'm making absolutely sure I understand exactly what I'm doing...

The query is about the details of opening the cooler thermostat. The guide sequence (text truncated by me) is:
"11: Fill to spill.
12: Start engine, add more fluid until spilling again, do various gear changes/revs. (This accounts for the pump drawing oil from the sump and pumping it through/around components)
13. Run engine until oil gets above 69C. (opens the thermostat)
14. Replace fill port finger tight, allow to cool below 30C.
15. Start again, remove fill port, fill to spill.
16. Lock off at proper torque settings."

My query is, the 'replace fill port' at (14) implies that I've left it off up to then. Should I be adding more fluid once the thermostat opens after (13) before switching off/replacing the fill port? Presumably fluid levels will drop as it fills the heat exchanger elements of the system? Or is that all covered off by filling at (15)? Or am I wrong, and should have put the fill port on finger tight before running up to 69C? (which is what I'd be tempted to do, but maybe fluid expands and drains out in this step?)

Grateful for all comments before I mess with this particular component... And yes, I'm using ZF LG8 - the cost per km against (say) Penrite ATF is lost in the noise, as against the peace of mind using the definitively correct fluid...

[DiscoJeffster]

You’re talking 8 speed I’m guessing by the fluid. I’m not sure if its procedure is different but the ZF method for the 6 speed is to monitor the gearbox oil temp until 34degC, with the engine running, keeping it so fluid is just running out and once at 34 degC, seal it up. You also have to run it through a few gears as well as part of the process (foot on the brake!).
If you stop the engine between these processes, seal it up else it’ll all spill out.

[PerthDisco]

You finger tight doing it up between initial fill and final fill once you’ve warmed it up and done gear changes then tighten it down

[Dagilmo]

You’re talking 8 speed I’m guessing by the fluid. I’m not sure if its procedure is different but the ZF method for the 6 speed is to monitor the gearbox oil temp until 34degC, with the engine running, keeping it so fluid is just running out and once at 34 degC, seal it up. You also have to run it through a few gears as well as part of the process (foot on the brake!).
If you stop the engine between these processes, seal it up else it’ll all spill out.

Having done both, it is a different procedure. The 6 speed much simpler.

It's been a while since I did my 8 speed. IIRC (and I possible don't) I left the plug out until 69 degrees. I had fluid seeping out during this time so no option to add more. Happy for anyone to correct this as it was a while ago I did it.

What I do remember well it it takes hours to cool to 30. I'd advise to start in the morning and go off and do something else and come back to it in the afternoon.

[Eric SDV6SE]

Easier with the car on 4 axle stands. Gets the torque converter correctly filled.