may alternatively be symmetrical i e having the same pitch on both sides and that the threads 46 of the worm 42 may instead be asymmetrical thus achieving the same directionally dependant efficiency relationship described above in another alternative an embodiment of the worm gear is contemplated wherein both the gear teeth and the threads of the worm are asymmetrical not pictured referring back to fig2 a and 2 b the gear 22 is oriented deliberately within the power window assembly in order that the worm 30 engages the sides 28 of the gear teeth 20 having a lesser pitch when the worm 30 rotates to raise the window and engages the sides 24 of the teeth 20 having a greater pitch when the worm 30 rotates to lower the window therefore the gear 22 will receive torque from its cooperating worm 30 more efficiently when the window is being raised and less efficiently when it is being lowered the additional torque efficiency provided during upward travel of the window compensates for the additional load placed on the motor due to gravity by tailoring the gear tooth profile to a specific window the gear 22 is able to transfer the desired torque to raise and lower the window at the same rate despite the different motor load generally the heavier the.