Creaking in the shackle or in the drive shaft. Creaking in the shackles is probably over tightening the bolts, loosen em up a bit and throw some lube on the bushings. If its in your drive shaft then your pinion angle might be out of alignment.
I bought some djm shackles and they squeaked like crazy. if they are djm, you can't tighten them like the stock ones. The guy at djm said 35 pounds for the spring to hanger bolt. The hanger to frame bolt can be at factory spec. You also have to make sure you grease them well.
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