I have a player object that can move and jump. When it starts falling after a jump the fall speed is good. However, when the object falls naturally off a plane and down on a lower one it starts falling very fast. In fact, it reaches about twice the fall speed of a jump even though the jump is is twice as high as the cliff.
When you jump lamdsingspeed = jumpspeed. When you fall you fall by default with normal gravity, being Vector3(0,-9.81,0). You can change this by going to Edit > Project Settings > Physics
I just fiddled with the same. What I did is when the CharacterController is grounded. Then I adjust the gravity to (lets say) 2 so when the player falls of a platform he will not fall like a 2 ton rock. Then when the character performs a jump I turned the gravity back to normal so the player dose not go sky high.