Allison m15 gearbox

[doggy]

I have a Detroit 671 with a Allison M15 gearbox.
Have been having problems engaging the forward gear.My oil is being airated I think due to low oil level.
I have been told to overfill past the full mark on the dipstick, I have done this and when I check the oil when the engine is running it is at the low mark.
My issue is do I again add oil and have the oil level 50 mm above the full mark when engine is not running.
That just sounds just a little extreme.
Thanks
Doggy

[shakey doug]

The level should be at the full mark at idle or immediately after shut down. Some installations have a remote cooler or large dia pipe work requiring a greater oil volume.

[doggy]

Thanks shakey doug
That was what I was thinking