Question: on a sealed 6 speed transmission/125,000/ can you change part of the fluid by dropping the pan/or is the whole unit one piece. thanks wordman

 

You will change most of the fluid by dropping the pan, some will be trapped in the tc and cooler.
Most people use about 6-7 litres to refill.
The filter is part of the pan so you should change that also and the electrical sleeve which is prone to leaks and can only be changed by removing the pan.
A search will yield lots of info, pay attention to the fill procedure, it's crucial.

 

Check the HowTos because they're really good on this. Expect to break the pan but plan to replace it anyway. Check you can undo the FILL plug first!

 

Also when you're undoing the pan securing bolts (#27 torx IIRC) they often break or strip the torx drive recess in the bolt due to corrosion. A top tip is to TIGHTEN them first until you hear the bolt 'crack' loose, then undo them.
This works due to the corrosion particles being loosened one way, then reversed again which breaks them up into smaller particles rather than acting like little teeth jamming the bolt thread in the gearbox.

Mine came out fine so I re-used them. There are #40 torx bolts available but as mine all were ok I just copper greased them and put them back in without any more expense on new bolts.

 

Good advice there! The slightest tightening can work wonderfully and for the reasons given.