I had my local dealer mechanic change from standard (progressive 440)springs to heavy duty..as I didn't do it myself I can only report that he did it "easy job" in about 15 min. they work great now...he also rebuilt my tranny (factory admitted to some assembly/shaft problem) that is now shifting very smooth with much less "klunk" than before. Work quality definitly depends a good mechanic and factory response depends on quality of the dealership rapport...good luck