I want to know how much torque is needed for the steering servo. specificly for a 1/10th scale 2wd truck . what does torque effect? Any help would be great thanks

I would say around 90oz. Think of torque as strength.

+1

The big thing or difference between torque ratings of steering servos is that the stronger the servo, the higher the torque rating, the easier it is for a particular servo to keep the wheels of your car aimed in the direction you have it intended to go under load - like in the turns. Stronger servos also take more abuse.
If you get too puny of a servo the wheels will want to straighten or re-aim themselves in the turns from outside sources, like the dirt or mud or berm you're trying to turn through. While a stronger servo will not as easily be affected.
It's always been my theory to have as strong/highest torque of servo as will fit in a vehicle so the car/truck will turn as need regardless of conditions, AND will not be as easily broken when landing jumps at odd angles or from the normal beating and bumpings or RC racing.