Can I use 75G D44X Cherry Microswitches in a Sanwa JLF? Will they be silent?

It is it technically possible to install Cherry D44X 75g .187" microswitches into a Sanwa JLF-TP-8YT, or Sanwa JLF-TP-8Y-SK joystick by removing the TPMA PCB and using a .187 to 5 pin conversion harness.

See below photo for install example.  We used to sell a kit that used D2RV-G microswitches and a Kowal 1mm Oversize Actuator for Sanwa JLF Series Joystick.

Silencer kit used D2RV-G microswitches.	Underside of silencer kit

That said, there are two things worth noting.

1. While the 75g D44X is very quiet, is cannot be regarded as "silent".  Your view of what is regarded as "silent" may vary.
2. Neither the Sanwa default actuator, nor the Kowal 1mm  oversize actuator was specifically designed for the D44X.  We cannot guarantee that these actuators will effectively engage with the much lighter microswitch plunger of the D44X in the same manner as they do with the default microswitches.  You will have to try this for yourself and determine whether the controls work as you prefer.