Driver swing weight question

DeeBee30 · March 15, 2019

I'm looking for some insight on how a driver with different swing weights *might* affect my swing and resulting ball flight. I currently play a Titleist 913D3 with a stiff Aldila RIP 60 shaft and Golf Pride New Decade MCC mid size grips. I don't know what the swing weight is - it's basically factory stock plus whatever weight the mid grip adds.

During a recent fitting, I was specced into a set of irons (D4 swing weight, which is the same as my current irons), and a TaylorMade M5 driver: 9.5*, Fuji Speeder Evo II 661 stiff shaft, and the same GP New Decade mid grip. **BUT**, the driver I hit in the fitting and was specced for was for a D7 swing weight. I'm already planning to go back to the fitter to understand why and to attempt to see what a D4 version of that setup would feel like. FWIW, my driver swing averages about 103 mph, with a slowish tempo and a fairly smooth transition at the top, and my natural miss is a bit of a pull hook due to some combination of not rotating my hips, shutting the face and a slightly negative swing path.

Generally speaking, how might a difference of 3 swing weights typically manifest itself in terms of impacting the swing?