Does "getting a lot of scratch" mean you're using a pick? Or is it just the left hand fingers sliding on the strings?
At least one acqauintance, who plays bass guitar in his group but regular guitar for most of our informal jams, uses a noticibly different technique on the bass. He seems to lift the left hand fingers clear when moving betweeen positions on the bass, more like I'd expect with a standup bass - more of a "jump" to the next fret than just a slide. Maybe he's just adapted to get rid of the "slide" noise?