The ornamental design for a shiftknob for automobile, as shown and described.
FIG. 1 is a front elevational view of a shift knob for automobile, in accordance with my new design, a second embodiment that is a mirror image thereof is not shown;
FIG. 2 is a rear elevational view thereof;
FIG. 3 is a top plan view thereof;
FIG. 4 is a bottom plan view thereof;
FIG. 5 is a left side elevational view thereof;
FIG. 6 is a right side elevational view thereof;
FIG. 7 is a front side perspective view thereof; and,
FIG. 8 is a rear side perspective view thereof.
The broken lines illustrate portions of the shift knob for automobile that form no part of the claimed design.