Are 7 inch long (bolt to bolt) shackles stupid long for the rear springs? I have two reasons for going this long...1) with my heavy rear bumper I'm 1 inch lower in the rear than the front 2) I have driveshaft vibration when I'm coasting which tells me my rear pinion angle is slightly too low.
I have 5 inch shackles now. By going to 7 inch shackles I can lift the rear 1 inch and hopefully cure my vibes. I don't know if 7 inch long shackles are stupid though.