Power gear
From Stunts Wiki
Some cars in stunts have the ability to reach a so-called 6th gear. This usually happens while driving in the last official gear with a high RPM, and doing a jump. Some cars can reach it from any speed, when driving on a loop, and shifting to the last gear. 6th gear allows cars to go a lot faster than the given maximum speed. Some cars have a so called: "true 6th gear", and they don't even slow down on grass, when driving in 6th gear. These are: ...
Others simply have a higher maximum speed than stated, which can be reached by the above described way. These are: ... Finding the 6th gear spots on a competition track is the key to victory. 6th gear was officially confirmed by Stunts lead programmer Kevin Pickell as a programming bug.