I have a mammoth st witch to me is heavy. Its a 1/8th scale truck. I bought a brand new HS-625MG thinking that could handle it. When the truck is on the ground, the tires don't even move. The screw unlocks itself and I end up spinning the screw and not the arm. I was told the HS-5955TG would solve the problem. Its a big step going from a $40 servo to a $115 servo. Do you think the HS-5955TG would be over kill for my truck. What would you recommend?

hey there mammoth , the cheapest most bang for your buck servo for a heavy truck would be a hs-945 (nondigital) or an hs-5945 (digital) . those servoes are 80 $ at your LHS or any hitec servo with at least 180 oz. of torque
later, Monty

Thanks for the info but what is the difference between digital and non.

The biggest difference between digital and analog servos are centering accuracy and holding power both in favor of the digital version. For your application the non digital version should be plenty. On a large 1/8 scale truck like this if you want to be able to move the wheels whith the vehicle stationary, probably the only servo that will do that is going to be the 5955TG. There is a lot of statc friction for the servo to over come to be able to move the wheels back and forth while the truck is stationary. Unless you are rack crawling this is not necessary as otherwise the vehicle is always going to be in motion when you are turning and the forces are much less at this point that the servo has to work against to move the tires.

BTW, the 945 and 5945 series servos were replaced with the 985 (analog) and 5985 (digital) servo so this should be the one to look for.