I know this has been written about several times but seem to find contradicting information in different threads........OK, I've got a 2003 F-150 SuperCrew. Just installed 2" dropped shackles. I haven't noticed any vibration but my driveshaft sloped slightly downward and my axle pinion shaft comes out pretty much straight in line like even with the truck practically straight out . From what I've read you want to have your driveshaft and axle pinion in line with each other. If so I've read that the rectangular plate under the spring pack is a stock shim and you can rotate this to correct this, true or not? I've also read that when you install the 2 degree shims that some places I've read say install with thin part forward and other say install with thick part forward, which is correct? To me you would want to install with the thin part forward so that my axle rotates upward to become even with the driveshaft. One more thing, If you do replace with the 2 degree shims do you remove that existing rectangular plate on the bottom or does it stay............all replies appreciated, thx.