I have the same issue with my Navigator as in this thread. I did the "hang" test, and sure enough, only goes clockwise, and thus, the hose becomes all twisted. I blew into the little hole in the gearbox, and it DOES make the 'whirring' sound, so I put it back together and it still twists the hose. I now have it in all apart on the bench again. It seems that the larger gears also are fine, and turn correctly.
Is there another thing I'm missing that could cause it to only turn one way? Should I get a new gearbox anyway, and try that? I did a whole A-frame, etc., replacement last summer and it was working great up until a few weeks ago with the twisting. The only thing I didn't replace was the gearbox, and the unit is about 5 years old.