I claim the ornamental design for a drive unit, as shown and described.
FIG. 1 is a left-front perspective view of the drive unit;
FIG. 2 is a front view of the drive unit shown in FIG. 1;
FIG. 3 is a rear view of the drive unit shown in FIG. 1;
FIG. 4 is a left side view of the drive unit shown in FIG. 1;
FIG. 5 is a right side of the drive unit shown in FIG. 1;
FIG. 6 is a top view of the drive unit shown in FIG. 1; and,
FIG. 7 is a bottom view of the drive unit shown in FIG. 1.
In the drawings, the broken lines depict unclaimed subject matter only and form no part of the claimed design. Any surfaces of the design not shown, including interior surfaces, also form no part of the claimed design.