The ornamental design for a primary drivechainhousing, as shown and described.
FIG. 1 is a front perspective view of the primary drive chain housing showing the new design thereof;
FIG. 2 is a front perspective view thereof as seen from the bottom;
FIG. 3 is a front elevational view thereof;
FIG. 4 is a left side elevational view thereof;
FIG. 5 is a right side elevational view thereof;
FIG. 6 is a bottom elevational view thereof;
FIG. 7 is a top elevational view thereof; and,
FIG. 8 is a rear elevational view thereof.
The broken lines showing various other features of the primary drive chain housing throughout FIGS. 1 through 8 are for illustrative purposes only and form no part of the claimed design.