ARGH!!!! did 14 FF swap on rear and can't seem to pin down a driveline vibration! Flange location from old axle to this one was the same, so no length issues on the shaft. Have rebalanced/rotated wheels/tires, all new brakes back there and 1 new drum, had shaft balanced today.... and it's still there. Not too noticable until 55+ or so, but I think it's there at the lower speeds as well. Axle flange does have 1 of the 'ears' that locate the u-joint a bit worn, but I set it to the other side when installing the u_joint caps. He (at balance shop) said a GM part nr 26020811, and a price of $160. (O U C H !!!!!!!) Heavy 3/4 ton - 1 ton flange? Before I raid my piggy bank and last remaining beer money, has anyone else experienced this fun? did the flange help? Is there something else obvious I'm overlooking?