Gripping the golf club too firmly causes a player to have lots of tension throughout their shoulders. Anytime your hands are too tight, you can feel the pressure running all the way up your arm. Too much tension in your shoulders makes it extremely difficult for most players to swing the club on the proper path. Typically, this pressure causes a player to swing ‘over the top’ of their shot, leading to a big slice. Nobody enjoys a big slice.
Another negative effect of too much grip pressure is a lack of club head speed. When you grip the club too firmly, your golf club isn’t able to release with any speed at the bottom of your swing. You are always ‘holding on’ and pushing the club through the ball. This causes you to hit at the golf ball with your body and shoulders, and that creates very slow speed. To better illustrate this, pick up a baseball and grip it as firmly as you can. When you do this, it becomes very difficult to throw with any velocity and accuracy. It’s hard to even let go of the ball. Once you relax that pressure on the ball, you throw with greater speed and accuracy.
Sam Snead was well known for his thought of gripping the club “as though you were holding a bird.” Though I understand this concept, this isn’t necessarily the clearest way of thinking about this. After all, how many of us have ever held a bird? Instead, I like to have my players focus on maintaining an awareness of the ‘heaviness’ in their club head. The club head, after all, is the heaviest part of the club. As long as you maintain your sense of feel for this, your grip pressure is fine. Generally, you don’t need to do much more than relax your fingers a bit.
If you continue to struggle with your grip pressure being too firm, try to start with relaxing your fingers while you chip and putt. This will allow you to develop a better sense of feel for the club head, and you can eventually begin to transfer this same feeling into your longer shots.
Learn to relax those hands, and the game will be more fun.