Hi there, if you only have a two channel remote you will need a reverse mod with mixer part number (tower hobbies site)LXMCX3 if you have a 3 channel you will not need the mixer, you will also need a standard servo part number HCAMO149. these parts come with detailed fitting instructions which make it very easy.

The mixer`lets you engage the reverse by just holding on the brake for three seconds and then the same again for back to forward , this is a safe system to use because there is no chance of putting the truck in reverse while it is still moving forward there by stopping any damage to the gear box.i have found it pays to compare prices with different sites, Hope this helps.