try this mine did the same thing passenger side...if u have independant suspension most likely ur half shaft stripped out...roufly 300 fix...on the independants you have a cogged shaft comeing out of your axle tube on the front end drivers and pass side which if you have ever worked on a front wheel drive car a peice like the cv joint goes overtop of that cog instead of into the axle housing like a car does then goes to another that attaches to the wheel via the half shaft mine stripped the axle and the cv joint and sounded like a chain rattleing if u have to replace the half shaft might as well while your at it install a new oil seal in the axle tube....


thats what i learned of a chain dragging noise on passenger side... i discoved the problem myself quite easy

jack up rear end off goung 6 inch of so put it in 4wd and hold brakes a little bit incase to slip and to put a lil more strain on front end and try to accelerate forward or reverse if the truck doesnt want to move and u hear grinding ifs the axle shaft stripped which inadvertantly strips the cv joint

mine would catch at higher speeds and chain noise would go away but not always

 

oops

 

ILL BE SURE TO CHECK THAT AXLE TONIGHT!!!