I found the following on my 99, this may help, may not. I found the back of the light assembly when installed rubbing the body. One side had more clearance then the other. It has been a while, 99 when I found that so I cannot remember exactly what it was hitting, but it solved my problem. I call it Silverodo i-test cause 30-40% of those trucks have one running light lit. Over voltage burns out a bulb, and both bulbs are on the same circuit.