The spindles are sent off to Airwolf Aerospace where they are machined (shortened). This removes the threaded end of the shaft where the Lamiflex Bearing is attached. Notice the difference in length between the two spindles in the photo to the left. Replacing the Lamiflex and the giant nut on the grip end of the spindle is the TT or Torsion Tension strap labeled #25 in the diagram. You can see it sticking out the end of the spindle. Now, instead of the centrifugal force pulling on the Lamiflex Bearing and a giant threaded nut, you have that force pulling on a pin (#32 in the diagram) that passes through the end of the TT strap.
My understanding is that the few spindles that failed due to cracking did so at the threaded end where the giant nut attaches them to the blade grip. By machining that section off and using the TT straps you eliminate the piece of the spindle that failed.
All new Enstrom Helicopters leave the factory with TT straps. Most older Enstrom Helicopters will be retrofit with them in order to comply with the spindle AD. Touted benefits are less maintenance and rotor blades that stay in track much more consistently than with the old Lamiflex. Time will tell and I’ll be sure to let everyone know how they work for me going forward.