Paul There are probably only two ways to get a ridge on one side, if your blades are good (sharp and not bent).
It could be one side of the deck higher than the other and that you would have caught when you did the deck leveling.
The other way would be like David says, the deck is bent where the bearing housing mounts.
This is my method for leveling a deck.
1. Turn the deck upside down and with new or known good blades, remove the belt and turn the blades till the tips are near each other. They should be the same height at that point. Then rotate one blade 180 degrees and they should be the same again. Check one side against the middle and then the other side against the middle. If they are off by 1/8 to 1/4 at this point it will make a large difference at the other end of the blade.
2. If the previous check was good I will use a level and a couple of large nuts and place the level with the large nuts on the center blade and using blocks of wood level the deck so the center blade is level forward and reverse, and side to side. Once it is level I check the two side blades to see they are also level.
3. If you find the blades off on either the first or second check you need to either straighten the deck to get you spindles correct, or use washers to correct them.
4. When I know the deck blades are level I mount the deck on the tractor. Check the tractor tires for correct air pressure and park on a flat concrete area. Then I cut a piece of wood, like a 1 x 3 to the height I want the blades. Set the blades front to back and adjust the height so the blade just touches the wood block. Turn the blades side to side and check the height with the wood block.
5. When you are done you will have the nicest looking lawn around.
