01 Silverado, 6.0L blazayblah w/ a 4L80E/PT Yank 3000 installed. The truck can be running and sitting still and when you put it in drive all is well. If you try to go past drive, I hear a loud squeak like right when the shifter is midway between D and 3. Doesn't make the noise if putting the shifter in 2 or 1.

If you put the shifter from 3 to D then it may just be a loud quick squeak or it may be a 2-3 second squeak that's extremely loud. I have no idea what the heck it is and it's not a problem when driving normal and just throwing the truck in D and heading out. Part throttle shifts are great and wot shifts always chirp the tires on the 1-2 shift and snappy as heck on others.

Could it be the neutral safety switch not being aligned properly or is it something else? Any ideas would be greatly appreciated! Thanks!