Will not go down all the way due to the way the rear door is made to accommodate the rear wheel well as 130artdeco has stated. Got to remember the door frame is wood and is about 3" thick in the area above the wheel well arc and that limits the amount of travel for the window plus a rubber stop about 3/8" thick on top of the wood. Have a picture of the inside of the door from a 1928 Fordor attached