Relocated Rear Suspension Shackle Mount
The theory behind this modification was to allow the shackles to fully "swing" as the suspension compresses and extends. When I originally installed my rear 4" Skyjacker SoftRide springs, I was using the stock length spring shackles. On full compression, the spring was able to nearly fully flatten and the shackle was extended out horizontally, actually allowing the spring to compress against the frame.
I then installed 2" longer custom shackles, thinking I would get a bit more travel. On extention I did, but I discovered that on compression, the shackles no longer ended up horizontal. My springs were flat, but the shackle still was angled down from the frame. Since I had added about 2" to the length of the shackles, I decided that relocating the frame mount about 2" further forward would allow the shackle to travel through it's complete range of motion. This will allow not only further compression, since the springs now flatten with the shackle, but also greater extention. Greater extention occurs because the shackle is 2" further forward, and the springs need to arc more as the shackles swings on extention.
The procedure is quite simple. Support the frame on jackstands and removed one rear shackle. Torch off the two rivets and grind out the welds (I used pinpoint weld cutters and my air tools). Remove the bracket...you'll likely need a pry bar to get it loose. Grind the mounting surface of the bracket to clean up the old welds. Grind the rivets flush and clean up the leftover welds on the frame.
Drill the forward most rivet out, first with a pilot bit then with a 3/8" bit. Using a 3/8" x 1" fine thread grade 5 bolt, attach the mounting bracket using the REARward bracket hole. This relocates the bracket @ 2" further forward. Square everything up and drill a new forward frame hole, again with the pilot and the 3/8" bit. (You will want to remove the bracket so it's out of the way. Also, the drill is a tight fit with the springs still installed.) Re-attach the bracket and tighten the bolts. (I used 2 flat washers, a lock washer, and red locktite) I did not reweld the brackets, however this is an option.
Check the difference in angle between the original setup and the revised location....the shackle angle has changed quite a bit. The final advantage to this is your ride....a verticle shackle will have a harsher ride than an angled one since the spring is essentially compressing against the shackle, instead of the spring and shackle compressing together against the frame.