Ill bet money its the one out by the wheel on the end of the axle, ive done mine which squeeked terrible! Dads 06, His friends 06 and another 06...all had 70k or less on them. dad got 38k out of his joints. So what i would tell you is to just do them both, replace with greaseable joints and be done. We put our trucks on our hoist got the torch out, cut the crosses out (make sure you have water ready cause the rubber and grease burns) Spin the tire and we used an air hammer to get the caps out. cleaned the area and let it cool, install new cross and tap new caps in. Dont even have to take the tire off. Done it to 4 trucks now....took about 2 hours each.