Well, if its the older model and its stock that would be your first mistake. Don't get me wrong, its a decent truck, but has is issues. The stock servo is worthless. Even if your running/moving the stock servo struggles. It's only 50oz/in which means its about 1/4 of what youd want ideally. And if they gave you Nimh or NiCd packs that are old and been sitting for ever that could be your next issue. Also the motors could be worn out too. But I would guess crap batteries first.
Cheap fixes that are direct fits
This is a direct drop in. The servo horn(the piece that goes onto the servo) is the same number of teeth. (different makes use 23,24 or 25. Your TRAXXAS servo is 25 as iis this one
http://www.valuehobby.com/radio-syst...hd-1501mg.html
VERY cheap, but reliable and over 200oz/in of torque
I would normally suggest lipo batteries. But being completely new maybe Nimh would be best for now.
With lipo you would need a LVC(low voltage cut off), new charger, change plugs.
Maybe put a "Wanted To Buy" add for some decent 6 cell Nimh packs with standard Tamiya style connectors. If your trucks all stock then it has the white plugs still. Maybe someone will sell you some decent packs cheap. Decent Nimh packs are expensive and arent worth the cost new.
I'll PM you. Check your messages at the top right corner for PM's! I'll help ya whener you need.