Grav, tell them it's for a 100 ton truck!
The engine input shafts to the transmission, and all the TR shafts use the Lucas (now Goodrich) couplings, so you can get up to about 3000 HP at 18,966 rpm. They are a marvel of new material science. Each is made of basically two Ti disks with flanged lips that are welded together. The drumhead of the disk flexes to take up the angular deflection needs, and the deformation is within the infinite life regime for the material. To prove that, each one is spun for 10e8 cycles at max deflection prior to delivery, proving them fit within that boundary. Where more than about 1.5 degrees are needed, two are used in series.
They are very light weight, basically just .050" Ti disks about 7 inches in diameter. The Apache also uses them. No parts, unlike Thomas couplings, which have many parts and many layers, and that slide against each other (fretting and cracking are the issue there.) the Thompson couplings are very nice design, but too many parts and complexity for simple shafts, IMHO. Could they replace the intermediate and tail GB?