Originally Posted by CJ82Sky
Lots of trot work to the weaker direction will help. In addition, one exercise my dressage trainer has me do that I do with students is to post on the WRONG diagonal, switching diagonals every so often when riding in the weaker direction to help the horse use their hind end evenly. It sounds weird but it really works!
I agree and also use this exercise with students and also young, green or unbalanced horses.
The other thing I would reccomend is doing extra in the 'bad' direction. Just because he's balanced, doesn't mean he's conditioned.
I would perhaps ask the vet next time he's out to take a look. If there is that much of a noticable difference, I would be concerned about an underlying weakness or problem causing him to over compensate on one side and not use himself on the weak side. Keep in mind, there can be problems going on that don't display in actual visual lameness....
What type of work are you currently doing with him? Can you describe what a typical workout might consist of?