Earlier 33 steerings were 13:1 until changed to 15:1 during the year. If you have a 13:1 worm/sector (same as 1932) the steering will be very quick, but very difficult. Changing to 15:1 gears is highly recommended.
If the end play on the worm gear is more than zero, the worm gear can get out of position and bind. It should have no pre-load and no end play. The gears should have zero lash at center, but will have play in either direction, as they are made that way so as they wear in the center, they can be re-adjusted without binding off of center. If with zero lash at center they bind off of center in both directions, the gears may be worn too much and should be replaced. There is also another
adjustment for centrilization of tooth contact to equalize play off of center, which may cure binding if it is in one direction but not the other.
The steering housings need to be made leak-proof. In addition to adding the seal on the sector shaft as CW advises, the oil tube that goes up into the shaft can come loose in the bottom plate, allowing oil to run out into the lighting switch. The tube needs to be soldered to the plate. Once made leakproof, heavy gear oil should be used as stated on the filler cap. STP is not heavy gear oil and may not properly migrate to where it is needed, nor will grease. Lack of proper lubrication can cause gauling, binding and the noise under load that you describe.
Even with the original sector bushings (properly honed/fit to the sector shaft - if the sector is loose, binding can result) if all of the above is properly done, the steering should be smooth and quiet. We have built many many with 15:1 gears (the latest gears from Argentina seem to be ok, so far...) and they perform very well. Adding the needle bearing at the top of the column as recommended by CW makes a huge difference. We use a bearing with a separate race that presses onto the steering shaft, and install the bearing into a rubber bushing (the currently available one without the bronze bushing) that is modified to fit into the column tube, thus insulating everything from the tube.
There is a chapter in the 1932 Ford Service Bulletins that provides excellent instructions on overhaul and proper adjustment, which also applies to 1933
and 1934. 1935 and 1936 are also of similar design.