One-Piece or Two? Why the 2015 Mustang Still Has a Two-Piece Driveshaft
It seems like a very simple piece of the drivetrain. The driveshaft transfers the torque of the transmission to the differential, so the rear wheels can drive or, you know, do burnouts. However, the 2015 Ford Mustang will not come with a single-piece driveshaft despite being an IRS layout. So, why, if the driveline angle will never change, will the 2015 Mustang need a two-piece driveshaft?
There are several factors in why an IRS car will use a two-piece driveshaft. In the case for Ford, it’s mostly about NVH, or noise, vibration, and harshness. The driveshaft will create a vibration similar to what your tires do when they become unbalanced. A long, single-piece driveshaft will suffer that far more easily in comparison to two shorter pieces.
There is also a safety issue not many bring up. Why? Well, it’s only an issue that comes from using a one-piece shaft at speeds that your Mustang is supposed to prevent you from hitting with its speed limiter. Much like a crankshaft, your driveshaft has a certain rotational speed it must stay away from or it will create a resonance. This is known as “driveshaft critical speed” and when that happens, the driveshaft will tear itself apart. I’ve attached this quick chart from Precision Shaft Technologies to give you an idea on what those speeds could be.