An overview of some of the most popular Servonaut items for 1:14 trucks;
* ESC
Generally the Servonaut ESCs makes one able to run the truck very 'smooth' and controlled forward/reverse, giving 'max power' to the motor. They will not let the truck suddenly 'jump' forward, or reverse, when you just carefully hit 'the pedal', as one can experience with the MFC units. Also one will not have the problem that the ESC starts doing 'cut and restart' when the load gets heavy, as one can experience with MFC that are not able to deliver so much Amps through the system.
Will function for both 7.2V and 12V (11.1 Lipo)
S22 : the classic ESC, full brake automatically on when stick in neautral, then brake release as one move forward or reverse. Gives 100% power/speed forward/reverse. Needs 1 channel. Connection for brake and reverse light. To controll by radio the rest of the main front and rear lights, one need to ad the Servonaut ML4 unit (or other similar independed light switch module)
E22 : similar as S22, and same price range, but with cruise control. Also depends on ML4 to get all light functions. NB! the E22 got 100% speed forward, but 50% speed/power in reverse. Can not be adjusted. Not recommended if often need reversing up a grade with a heavy load. But for 'normal duty' on good roads, no big issue.
Needs 2 channels; one for changeing between forward/reverese, one for speed (the 'pedal') usually hooked up to the left joystick; move the stick down and left/right for change forward/reverse. Let the stick in neutral and the truck will stand still.. as one move the stick forwards the truck will accelerate (as long as the stick is hold somewhere in forward position) When reached the speed one wish, one let the stick back in neutral. Now the truck will move in a certain steady speed forward (or reverse), until one move the stick backwards to de-accelerate.. Will stop when move the stick all the way back, and let it in neutral again) It's a matter of habit, not difficult to get into) Many remove the spring for the 'speed' stick, letting the stick sit all the way back in neuatral position. The advantage is that one are able to make the truck keep a more stable speed, looking more realistic too scale.
M24: ESC with cruise controll (can be turned off and funtion as S22) and fully possible to control main lights front and rear (no need for ML4 or additional modules to control lights) Have some additional settings that one not find in s22 and e22, as adjusting the level of brake power etc, programming between Xenon / standard light and more, but otherwise same basic functions, 100% forward, 100% reverse.
* Sound modules;
The sound modules uses some different speakers, different ohm, varies with type of unit, and 7.2 or 12v, it's specified what to select by the supplier.
SM3 : the basic sound module, one can change between some different engine sounds. in addtion horn, brake,
SM7 : more advanced than SM3, but they got same quality of sound. One can do more programming of the sounds, change the sound level of invidual sounds like turbo, horn and so on.
* Gear motors:
GM32U390, 7.2V (GM32U450, 12V, 50% more power than the U390) More power, less sound, less 'play', take less space than the original Tamiya gearbox/motor. There is a seperate mounting bracket needed for the GM32 motors, UAT1, or UAT2. One of the most popular upgrades in Europe; getting rid of the orignal bulky Tamiya transmission. After some time, many drivers see that it's not that important with 3 gears on such a model truck, more of a sales trick from Tamiya that makes a good picture on the box, as one usually just drive around slowly in 1'st gear anyway to be able to have good control. There is natural the matter of cost and upgrades. If one most have the truck placed on the shelf, no need to do much upgrade, but more active drivers enjoy to look into some upgrades. Among the reasons many trucks sits much time on a shelf, is possible that the owners think that they are not so 'drivable' in original edition, and are not aware of the good upgrades out there that can really change how the truck operates to the better. but yeah, it costs, like most hobbies
When talking about drivability, check out RC4WD soft tires, Hauler, Roady, makes a huge difference comapered to the original tires.
There is also variants of the GM32 motors with a transfere case built-in, for driven front axle(s). Suits great with long wheel base trucks, as the US trucks, both not for the short wheel base Euro rigs (and Globeliner) In those cases it is adviced using the basic gearmotor and a stand-alone transfere case.
* Servonaut also offers some of the highest quality front/rear LED prints, mostly for Euro trucks.