Having a too weak or too strong of a grip can extremely affect your swing. Here are some of the characteristics of both…
A sign of a weak grip at address is when you are NOT able to see at least 2 knuckles on your left hand (for right handed golfers). The “V” that is formed between your thumb and the index finger is pointing at your left eye or your chin.
A sign of a strong grip at address is when you are ABLE to see at least 3 knuckles on your left hand. The “V” that is formed between your thumb and the index finger is pointing at your right shoulder or elbow.
Now, that is the basic instruction that you will see on any Google search you will find on the basic fundamentals of the grip. I want to take it a step further and also talk about how the shaft lean takes a part in this as well.
Now if you look at a weak grip, usually it is associated with at shaft that is too straight up and down or leaning away from the target. This person needs to first exaggerate a forward shaft lean and then find that balance.
Now if you look at a strong grip, usually it is associated with at shaft that is too far forward to the target. This person needs to feel the shaft stand straight up and down and then find a balance of how much lean then need. A person with a strong grip that has their hands too straight up and down, they with tend to have a huge cup form on the left side of the left wrist. This can be uncomfortable and is a sign that you need to place the ball further back of your stance or lean the shaft more forward.
As you can see, I don’t want to say anything about the “ideal” grip because you will think that it is the only way you can hold a golf club. Their are great players who have played with too weak or too strong of a grip and knew how to make it work. In your game, it is the adjustments you need to do in order to fit your preference. That is what golf is all about.