I did. I think it is the rear springs that is the problem. They flex really well but I may try something a little stiffer. I've been doing a lot of multi day trips recently and they don't hold up a fully loaded PU too well.

 

I noticed that my SAS kit came with the 3/8" weld on perch spacer but I didn't install it on my axle. It looks fine on my truck without it. BTW I am running a 1980 axle with 85 knuckles.

 

Problem is the spring perches on the front axle are not of equal height. Stock front springs are unequally arched and have different spring rates to account for the difference. Most aftermarket springs are the same (no left or right spring) and thus need the spacer to level out the perches and even out the load on the springs. While 3/8" may not sound like a lot, the perches are only half way out from the center of the axle and thus any difference gets multiplied by 2 at the wheel. And the uneven perch height makes for uneven load on the springs, making the passenger side carry more load (it is already loaded more than the driver's side statically) and that can make it sag faster. Often that unequal spring loading up front can be amplified at the rear of the vehicle, since the rear springs tend to have less weight on them and the spring rates are less. I welded a spacer on my front axle, but you can also bolt on to the spring pack to do the same thing:
- http://www.4crawler.com/4x4/ForSale/...ingPerchSpacer

 

Roger, Thanks for the information. I will try welding the spring pad spacer on my axle tomorrow and see if that helps.