John Kelly (Weber Auto channel) has produced a very-detailed video of a Mach-E gear reducer teardown while another recent video from S. Korea shows a less-detailed and perhaps more clumsy teardown of the Ioniq 5 unit. This technology interests me a lot as a mechanical engineer and Kona EV owner so I lap it up. Here's the TL;DR for the two videos: 1. Both use oil to cool the motor as does (for example) most Tesla models and the Chevy Bolt (and derivatives). Direct cooling by coolant combined with a "dry" motor and grease-lubricated motor bearings as used on the Nissan Leaf and legacy Hyundai/Kia seems to be on the way out. The advantage of the "wet" design is that it vastly simplifies the bearing arrangement and integration between the motor and reducer input. In both cases the oil is pumped electrically so that it can run while the car is stationary and use minimal power at high speed. 2. In both cases the reducers appears to be entirely splash-lubricated, the most common method with the exception of the Tesla Plaid which has supplemental pumped lubrication at the input pinion gear. 3. The Ioniq 5 is a parallel-shaft reducer while the Mach-E has a compound planetary gearset. The clever and compact Mach-E reducer has been designed by Borg-Warner and can be purchased for aftermarket use. 4. The Ioniq 5 has what appears to be a motor shaft grounding assembly (see left yellow arrow below) while the Mach-E video doesn't explain how that's done. 5. Oil filtering on the Mach-E is done by a serviceable intake screen but there's no mention if a magnet if fitted as well. It's not clear what filtering methods Hyundai have employed on the Ioniq 5 but there appears to be space for a small screen. I've indicated (right arrow) where an internal magnet could have been located inside the housing. It's the same casting detail seen on legacy Hyundai/Kia. Photo is of the Ioniq 5 motor-side reducer housing.
