Hope someone can shed some light on this one for me. I just got done putting my 14 bolt FF with detroit locker in last night. The background info is this: I had been running a 4" lift with Superlift springs up front and blocks in the back with a 10 bolt front and rear. This weekend I put in 6" superlift springs (warranty replacement) up front, ORD shackle flip and 2.5" springs in rear. Then the 14 bolt went in last night. Everything went together pretty smoothly and I hooked up the driveshaft with the new Neapco 5-1153X conversion u-joint, it all hooked right up. Here's the problem - driving home, ANY time I let off the gas when rolling there is a severe vibration and a "grinding" or "metallic" noise coming from the rear of the truck! As soon as I apply power it seems to go away, but as soon as I let off again it comes back. And it stays until very low speed. I got up to about 70, and it is pretty much constant until just before stopping...any ideas? I am going to bring it down to the driveline shop and have them check the angles, etc. The pinion is pointed up nicely with shims and the ORD shackles, but there must be something out of whack... Any help would be appreciated... can I rule out the Detroit locker? It was regeared and the locker installed by a reputable shop, but is that the next place to look?