reverse lights, not coming on at right time.

[dbmx66]

its an 84 k10, when i put it reverse (like actually feel the tranny shift into reverse) the reverse lights dont come on. but when its in reverse if i pull down on the shifter a slight bit, not enough to make it go in neutral though, the lights come on. but if i adjust the shift linkage, it wont go into other gears right. how can i solve this.

thanks.