Gerry, (Henderson, TN)
In addition, there is a locking nut positioned up inside the mechanism. Since you've had the gearbox already replaced, I doubt this nut has worked loose. You can try reinstalling that nut using some thread lock solution if it has, however. It takes a 15/16" deep socket to remove and tighten that nut. Winegard does have a tool that can also be used if you do not have a deep socket of that size.
Update! From Mike (an interested reader): Regarding your reply to the question on the ever-loosening crank handle on the Winegard crank-up TV antenna; I had the same problem. The malfunction was caused by the end of the spring twisting the crank handle holding nut loose. The factory should have installed a washer between the spring and crank handle nut to prevent the binding. I installed this washer and also installed another washer atop the spring to keep it from eating into the plastic on top. After I did this, the problem was corrected. Additionally, I applied a small amount of petroleum jelly to the washers to reduce the friction. The handle also cranks much smoother now. Hope this helps others!