The centre shaft runs on three ball-races for a true and wobble-free spur. This is however where the ball-races end since the rest of the drivetrain runs on metal bushings.

The lack of ballraces in the majority of the car cannot be a surprise for this money - but it would be the first upgrade if you want more speed.

The spur gear and motor pinion are protected from dirt and small stones by an upper and lower casing. The lower half of this casing slots into the chassis and is followed by the rest of the drive train. The top half of the casing goes on last - to completely seal the gears.

The motor is provided with a 20 tooth 0.6 module pinion (the same pitch as on many Tamiya kits). The motor secures to a plastic motor plate which in turn slots into the chassis. The mesh is pre-set for the 20 tooth pinion by special holes in the plate - alternate mounting positions in the plate enable you to change pinions and alter the mesh to suit different wind motors, if you choose to upgrade later.

The differentials on the BX-1 are self enclosed units and bear a passing resemblance to those seen in their larger scale nitro brothers.  This does mean they can be filled with heavy grease to slow down the diff-action and provide better traction. 
A-Tech do a good job of filling these differentials with some type of [smelly] grease, but heavier grease would be even better. Another alternative is 'Diff oil' like that used in the 8th scale class. After cleaning the diffs up and taking these photos I refilled the diffs with some 30k weight oil - the diffs aren't O-ring sealed, but the heavy oil doesn't leak - or at least very very slowly even with hard running.

Power is sent to all four corners via identical "Dog Bone" style drive shafts and axles. These are steel and look well up to the job - unlike those nasty plastic things on similarly priced Tamiya kits (without electrics!)
The axles run on metal busings and use Tamiya / Touring sized hex adaptors.

Front and rear, left and right, all the lower suspension arms are identical on the BX-1. This does make spares a breeze, though as previously mentioned - this plastic seems very reslilient so breaks should be few.

The suspension arms all pivot inside dual pivot blocks and use plastic balls on the ends of the hinge pins to allow squat changes and give a solid and secure friction-free mounting.