One thing we noticed when we had the transmission shifter off our NV3550 was that the unit didn't have any fluid in it. Normally Advance Adapters ships all of its NV3550s full of fluid to prevent the installer from filling with the wrong fluid, but we dropped in to pick up our unit before the company filled it. The fill and drain plugs are a 17mm hex socket, but the head of a metric bolt works equally well.
