I installed a Hurst Billet shifter in my 2009 Mustang Gt a few weeks ago, and developed a knocking/rattle noise under moderate to heavy acceleration only, which sounds like its coming from under the shifter.
A local performance shop told me after looking at it that is coming from the transmission. I checked the shifter, all bolts are tight, and the shifter is installed properly. The rattle is not coming from the shifter ball or the allen bolts that hold the shifter arm together, as i already checked.
The rattle only occurs under load, and not in neutral. My car is pretty much stock. I have not been able to find anything about internal transmission rattle, and i dont believe the rattle is the exhaust, heat shields, or engine pinging. Any advice would be appreciated.

 

I would contact Hurst to see what they think.

 

Aftermarket shifters can be louder, especially if you dont use the gaskets on the shifter handle linkage.

 

Are you sure it's not the ball? Put some red loctite on that ****** and torque the nutz out of it. That's what I had to do.