 Tharp, Budd and Trammell left the group in the early 1960s, but the Fireballs added Doug Roberts on drums, plus Petty Studio singer/pianist Jimmy Gilmer (born September 15, 1940 in Chicago and raised in Amarillo, Texas) to the group.Billed as Jimmy Gilmer and the Fireballs, the group reached number 1 on the Billboard chart with "Sugar Shack", which remained at that position for five weeks in 1963.The single also reached number 1 on Billboard's R&B chart for one week in November of that year, but its run on that chart was cut short because "Billboard" ceased publishing an R&B chart from November 30, 1963 to January 23, 1965.