I've been having the same problem with every servo I've ever had. For the most part these have been Futaba S148 type servos, but now I've begun buying higher end servos and have the same problem.

The problem is when I grab a wheel and turn it left and right they move back and forth. There is some slop in the steering components (TC3 modded, XXX-CR, RC18R modded) but 95% of the slop always comes from the servo.

The two higher end servos are Hitec HS-56 and JR Z590. The Z590 has been through about 12 5 minute runs and it already feels loose. The HS-56 has been through about 8 runs and is already feeling looser. Is it the bearings that are giving out? How often should these be replaced?