If you're planning to drive your hot rod or custom (and why
wouldn't you?) you need to make sure the engine, transmission,
third member, and driveshaft are all working together in
harmony. The piece of this puzzle that would seem to be the
simplest, as it has the least amount of moving parts, is the
driveshaft. We had a pretty good idea how to set up a one-piece
driveshaft, but the question of the proper method for a two-
piece unit came up, which also brought up the question of just
when a two-piece is necessary.  We decided to go to the experts
and ask. Greg Frick at Inland Empire Driveline told us the
following: "A driveshaft explodes at an rpm called critical
speed. In theory, critical speed depends on shaft length,
weight, diameter, and rpm. In the real world, critical speed is
lowered by U-joint angles, shaft mounts, and even the engine's
firing. Keeping safely away from critical speed affects
decisions about driveshaft tube diameter and the decision to use
a two-piece shaft set with the added support wh