Too late =X, already put grease in the cups. It helped a little bit, but it turns out that some of the rod ends had such a tight fit on the ball studs that they needed quite a bit of force to move around. So to fix this i exchanged it with other rod ends (bought 2 sets of 12). It helped a little, the servo still can't center the wheels after coming from left or right directions but it's definitely a lot better than before.
Now i'm confused about one thing, do servos use less power when coming back to neutral? Because it doesn't seem to have a problem turning the wheel; it had enough power to push the car, while on the table, away from my finger when i tried to prevent it from moving. After i release the the steering wheel on the transmitter, i have to manually push the wheels about 2 degrees back to neutral.