Thats the Komatsu 930E that uses the electric motors, the whole truck is electric for that matter.
The Cat still utilizes a rear diff:
The modular differential, also designed and manufactured by Caterpillar, is rear mounted within the axle to improve access for maintenance. The differential is pressure lubricated, which promotes greater efficiency and long life. Each final drive incorporates a nodular iron wheel for high strength and long life. Wide wheel beating spread reduces bearing loads and helps ensure durability, Cat said. A hydraulically driven lube and cooling system operates independently of ground speed and pumps a continuous supply of filtered oil to each final drive.
just a few numbers to crunch with these things
Final drive in the 797 is:
Differential Ratio - 1.265:1
Planetary Ratio - 16.67:1
Total Reduction Ratio - 21.09:1
Although many competitors use hybrid diesel-electric drivetrains (as the Dresser Haulpak 830E we tested in July 1992 did), Cat mining trucks are direct driven, using Cat-built drivetrains. The 797's powerplant is essentially two V-12s lashed together with integrated intake, exhaust, and turbocharger systems. Each of the 24 4.9-liter cylinders breathes via four valves and is pressurized by four Garrett 60-series turbos. From there, the resulting 3400 horsepower travels back through an immense torque converter to a seven-speed automatic transmission and then on to the 1.27:1 gears in the rear end's differential. The final-drive ratio is further reduced by 16.70:1 reduction gears in the hubs. Flat out, the 797 will do 40 mph.
here's a pic of what everything looks like when its in the truck,
Yes it looks small but who are we kidding, the rear diff in that thing IS actually larger then a ford ranger, an f-150 for that matter.
i've been pretty close to these things and pictures just don't do them justice heh, the motor needs a 15 ton rafter crane just to hoist it 13 feet into the truck.
Welcome Visitor! Please take a few seconds and 
