Make sure the tire pressure is correct then level the deck per the manual. Did you put the blades on yourself? Are you sure one is not upside down?

Ditto rager's reply.

Also - if you are cutting tall thick grass (taller than 4-5 inches) and having your deck at it's highest setting, perhaps you are seeing the effects of trimmed grass bent over by the passing of the tractor's wheels?

Thanks for the posts. The blades are oriented the same way as the original blades. The higher swath is exactly in the center of the cut midway between the tire tracks. It is cutting about as well as an old craftsman rider mower that I replaced.

Set at 4" inches, are you cutting with the deck on the transport setting?