Not sure about the 4 in, but I installed the 2 in four years ago and the springs are just fine. The only thing I noted is that I used the HD springs and ended up with about 3.2 in lift...you might get more also. Check with Dave at Northridge for
good details, but I doubt the springs will sag, and in fact, this is the first I have heard of this...now RC, then yes.
08 JK 23S - Colorado Jeep Club No. 204
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