Technical 2012 180 MULTIJET 3.0 GEARBOX SERVICE

[gleneagle]

I just completed an engine and gearbox service on my 2012 180 Multijet F1CE3481E 3.0L motor with Comfort-matic semi-automatic gearbox.
I used Penrite Pro Gear oil 75w85 during the gearbox service, Adding exactly 2.9L.
I drove down the road about 2 km and it started slipping on the hill. and started making a whirring noise which increased and decreased with accelleration. I only drove a few km to the shops then took the back roads home and tried to keep it under 40km p/hr. It "whirred" until it got to about 50 and then the noise went away, until i got to another hill and it again made noise and slipped.
Is this because the oil is too low ...even though I added to specified amount?
The only thing i can think of, is that i had my van on ramps while i was servicing it, and maybe this caused any extra gearbox oil in the lines to also drain out.
So how many litres is a dry fill? IS there a was of checking the level of the oil? There appears to be no dip stick!
Aside from the obvious noises there is an orange check engine light on....but it has no digital level check like it does for the engine oil?
ANy Ideas?

 

[gleneagle]

UPDATE : The weird noise is caused by a faulty PRESSURE CONTROL SOLENOID. Fault code P0748.
The gearbox was running fine before this so maybe it got saturated in oil. Its highly un-likely that it just coincidently gave up because it was jealous of the new oil. (Although it is Penrite.) The box has just done 100k. I will try pulling apart and cleaning all electrical componants.