i have 4.5 in the back and when i installed the D44 at full droop the drive shaft was locking. i discovered this this when regearing and arb'ing i had the 'frame' on jack stands and the axel hanging. at full extension i could not turn the shaft.. i had to jack the axel up about 1.5 inches to get the shaft to spin again. so now i have a sye installed ! lol