I claim the ornamental design for a drive unit, as shown and described.
FIG. 1 is a right rear perspective view of the drive unit;
FIG. 2 is a rear view of the drive unit shown in FIG. 1;
FIG. 3 is a front view of the drive unit shown in FIG. 1;
FIG. 4 is a right view of the drive unit shown in FIG. 1;
FIG. 5 is a left side view of the drive unit shown in FIG. 1;
FIG. 6 is a top side view of the drive unit shown in FIG. 1; and,
FIG. 7 is a bottom view of the drive unit shown in FIG. 1.
The subject matter shown in dashed lines, and any surfaces of the design not shown, including interior surfaces, form no part of the claimed invention.