The present invention relates to a speed control unit associated with a peanut combine for driving and controlling the peripheral speed of a forwardly disposed crop engaging pick-up reel rotatively mounted transversely about the front of the peanut combine. The speed control unit basically includes a dual input drive system including a first drive operatively connected to at least one ground engaging wheel of the combine for providing an input drive corresponding to the ground speed of the peanut combine. A second generally constant input drive is provided from a power take-off source associated with the peanut combine. These two drives simultaneously drive a centrifugal clutch which includes an output drive member that is driven at a speed corresponding to the faster of the two input drives. In controlling the peripheral speed of the pick-up reel, the clutch assembly and speed control unit is so designed that the pick-up reel is driven from the output drive member of the clutch assembly such that the peripheral speed of the pick-up reel is generally equal the ground speed of the peanut combine as long as the ground speed of the combine is at least equal to or greater than a selected speed. Where the speed of the peanut combine falls below said selected speed, then the second generally constant input speed from the power take-off source is operative to drive the output drive member of the clutch assembly and consequently the peripheral speed of the pick-up reel is driven at a relatively constant speed in this case.