is this caused by diff pull?

[blueb8llz]

how do i check if i have a bad steering servo. it still returns back to center , but only when i turn left/right very minimal then it doesnt. do i open up the servo and check for stripped tooth?
wheel bearings and driveshafts are all looking good. but to check the shocks was a good idea, never even thought bout it. but those are all good as well. im pretty sure also its not the shocks cus if it was one bad shock on one side it would always pull to that side right or no? in my case it would sometimes pull to the left or right just depending on how i just adjusted my toe in with the front and rear tires.
i kinda think its because the tires dont get back to center when i turn left/right very minimal because since the servos arent holding it in the center, as it gains more speed the tires shake a little more causing the tire/wheel to turn left/right just a bit. and when this does happen, ill turn it the opposite direction to make it go straight, but then it would just veer in that direction , instead of just pulling it to the other direction just a tad so i can be going straight. hope this all make sense to you guys.
just needa know how to fix that thing