By chance your box doesn't have "Flaming River" cast into the top? I have one on mine and I'm having similar problems right now. Through various internet searches I have discovered that Flaming River Vega style boxes seem to have a bad rep for wearing out prematurely. My car just turned 10,000 miles. 9000 were trouble free, but in the past 1000 I've had to adjust the slop out of my box twice.... and it still doesn't seem to be as good as it was when new. I'm thinking the box is headed south.