I took it out wheeling this afternoon and it did great. I wanted to hit some flexy stuff and check everything out underneath. And I had to test out the ride. It was a little stiffer in the back unloaded, but not anywhere near what I expected. The coils ride pretty nice. No hopping on washboard dirt roads, which really surprised me. But they are a little more springy than stock unloaded. I am sure they will ride even better with some gear and a passenger or two in the truck, which is what I did the mod for in the first place. I may have forgotten to mention that I did this mod to increase the ride height in the rear end while the truck is loaded for expedition trips with the wife.
Here's a shot of the back tire with the suspension almost fully stuffed. Before I relocated the axle forward, the tire was almost touching the rear of the wheel well when stuffed. Now it is a little closer to the front of the wheel well, but closer to centered than stock. If I were to install axle relocation plates on another toy, I would have 4Crawler custom build them to move the axle 1/2-inch forward instead of 3/4-inch.
And the other side at full droop. The tire is off the ground, even though it's hard to see it from this angle.
Here is why I went with a 10-inch spring. I didn't want excessive lift or the coil spring to be pressing down on the axle trying to extend the shocks, brake lines, etc. any more at full droop. You can see that the 1 3/8-inch tall bumpstop keeps the spring in place even at full droop when the spring has no weight on it. This also makes it fairly easy to remove and reinstall the coils, which I wanted to be able to do in case it rode like a brick unloaded. That way I could have taken the coils out for daily driving and popped them back in for the expedition runs with a full load of gear. An 11-inch spring would have probably been perfect for my setup, but since my only other choice was 12-inches, I went with the 10 and am glad I did. Note, without the one-inch lift rear shackles I am running, the ten-inch coils would be perfect on an otherwise stock rear end.
Here is a look at the coil spring on the side of the truck that is almost fully stuffed. Just a little bit of space left between those coils. I worried that the coil might excessively limit uptravel of the rear axle, but the rear suspension is still plenty flexy for the off-camber stuff.
These rear leaf springs have 95,000 miles on them and have sagged quite a bit from what they were when we drove it off the lot. Be sure you evaluate your specific setup before you make this mod to your rig. Also, if you are not planning to run these Add-a-coils with a load, but want them as a lift-kit only, I suggest you look around for some 100lb springs, to improve the unloaded ride quality.
I guess in retrospect, I wouldn't really do this any differently if I had to do it again (other than getting 1/2-inch axle relocation plates).
I will note that there is room between the top of the factory rubber bumpstop and the Daystar bumpstop at the top of the coil when almost stuffed with the opposite tire off the ground (but not much). Since the bottom of the coil rests on the factory rubber stop, I think that is fine. The two bumps might hit when stuffed with some weight on the rear end to fully compress the coils. There was not enough weight in the truck during my flex test to find out for sure. But if you do this mod and you want the two bumpstops to make contact when fully stuffed, you should buy slightly taller bumpstops for the top of the spring, I think a 2-inch tall stop would do it, but you'd better do some measuring on your rig before you buy. I used a 1 3/8" stop because I calculated that it would be plenty long enough to keep the spring from falling out at full droop, and the 2 1/2" diameter O.D. of the stop was perfect to match the I.D. of the coils I bought, which are 2 5/8".
Also, note that my truck already had a 2-inch longer (one inch lift) rear spring shackle prior to doing this mod. So my total rear lift on the truck is now 3 3/8" unloaded. Should be just about perfect with a full load of gear in the bed. I'll update this thread after we load up the truck and see how it rides loaded.
For reference... Sitting on worn 265 75R 16's on flat concrete the distance (measuring through the center of the wheel) from the ground to the top of the fender flare/wheel well opening is 38 inches. Exactly the same on both sides. The way my IVD Coilovers on the front are adjusted (1 3/4-inches of thread showing), this measurement is 37.5 inches on the front wheel wells.