It dosen't take much to get that working. With 2 motors, you don't need a transmission, just a hollow outer shaft with a bearing and another shaft inside it. Then you have 2 drive wheels on the back.
And it dosen't take much to cause friction there. Keep in mind that in your washer, everything moves on way.
There, you have 2 opposing rotations.
It's like a highway back on back vs a head on collission.