The Race Against the Mammoth Car (Part 1)

When Trixie was granted the position of Speed's assistant in the No Limit World Race, Inspector Detector and his officials search each entry looking for $50 million in stolen gold bars before the race begins. When The Mammoth Car enters the track, its driver gives the Inspector a tour, giving no single trace of the gold. When the race begins, the Mammoth Car forces everyone off the road, making Speed a bit suspicious. On it's way to discover the Mammoth Car’s secret, he equips the homing robot with X-ray film so he can be able to penetrate the metal.

The robot is shot at and returns home broken. Now, the Mammoth Car catches up to Speed and forces the Mach 5 off the road. When a ramp is lowered, a squad of motorcyclists descends onto the road. Racer X appears and spills oil on the road, causing the bikers to crash. At the airport, Spritle and Chim Chim stow-away aboard on Cruncher Block's airplane. Meanwhile on the road, the Mach 5 and the Mammoth Car both collide and veers off the road towards the forest. While Speed uses his rotary saws to cut down the trees, the Mammoth Car's power mows its own path. Speed turns around and tries to slash the car’s tires, but the Mammoth Car dodges it and encircles the Mach 5. Guns emerge from its sides. Speed closes the cockpit to block the shower of bullets and escapes through a gap and plunges into a lake.

Continuity Errors
In the English dub the Mammoth Car's driver brags that  the Mammoth Car can go over 500 mph (800 km/h) on any type of road. This is impossible as we see the speedometer of the GRX in a first part of the episode "Fastest Car on Earth" and it supposedly maxed out at  400 km/h (250 mph)  and latter the  speedometer of the Mach 5 in the second part of the same story which maxed out at  360 km/h (about 224 miles/hour). Yet Speed caught up to the  Mammoth Car twice.

Cast

 * Peter Fernandez: Speed Racer, Racer X
 * Corinne Orr: Trixie, Spritle Racer, Mom Racer
 * Jack Grimes: Sparky, Chim Chim
 * Jack Curtis: Pops Racer, Inspector Detector