Those Tesla folks are finally (almost) out of the woods on this whole powertrain nonsense. Its original two-speed design had many "durability, efficiency and cost challenges," but Tesla Motors decided to go with it in its first production run, and then swap in the new single-speed "1.5" powertrain once they get it just right. It's a bit funny Tesla 'fessing up to durability problems now, after denying them so vehemently before, but either way buyers of the first 40 cars that'll ship with the old powertrain won't have to wait long for an upgrade, since the 1.5 powertrain has been finalized and is slated for production in August. Tesla already has a 1.5 version they're driving regularly, and they're in the testing phase. 1.5 involves improvements to the motor, inverter and gearbox design, and improves torque among other things -- which gives that 3.9 second 0-60 spec they've always wanted.