Battery Connections/Exposed Wires
This is an often overlooked area when trying to protect your truck from the elements. You should cover all connections, such as battery plugs, that are exposed to the elements. Otherwise it's possible that moisture could seep into these plugs and short out the two wires. A few pieces of electrical tape should take care of this situation easily, just make sure to surround the entire plug as any small opening could be an entry point for water. Motor
Believe it or not, in an electric RC, the motor is an area that requires very little attention when exposed to the elements. You don't really need to worry about keeping the moisture away from the elements as water will not affect it's operation. As a matter of fact, in some cases hobbyists run a motor underwater as a way to break the motor in. The only thing you'll need to do is disassemble the motor after running, and clean it well. Make sure you re-lube your motor's bearings or bushings when putting it back together. Receiver/Receiver Pack
The receiver is generally one of the most expensive components on an RC truck, so you want to make sure you provide it plenty of protection from the elements. Many nitro-powered vehicles already have the receiver protected with some sort of cover or plastic box to avoid damage should nitro splash on it when refueling. However very few electric vehicles offer this sort of protection, and even in the nitro world there are some exceptions.
Many receiver boxes can be used on vehicles other than the ones they were intended for, when used with a little creativity. This provides a good option for protecting your receiver. When using a receiver or battery box, keep in mind there are often small gaps in them. Most of the time, these are the areas that wires pass through. It would be a very wise course of action to seal these gaps up with silicone to prevent water from finding it's way inside.
You can also use a balloon to cover the receiver if this option isn't feasible for you. Simply insert the receiver into a balloon, with the servos already plugged into the receiver in their correct locations. Then close up the mouth of the balloon with a ziptie. You can also seal up the mouth of the balloon with some grease or silicone to help seal up any leftover gaps after the ziptie is pulled tight. While it may not be the most attractive solution, it's very effective. If your truck also uses a receiver pack, or battery holder, to power the receiver you should also protect it as well. Again many trucks provide battery boxes, and those battery boxes can fit many other vehicles besides the ones which they were designed for. If all else fails, a balloon will work well in this area as well. Servos
Servos are another item that should be protected from the elements. Some servos, such as the Hitec 5625MG and 5645MG, are water-proof and need no further attention. However most servos do need to be protected from the elements. There are two widely used methods to accomplish this, balloons and silicone. Using a balloon is pretty straightforward. First remove the servo horn or servo saver, and then simply encase the servo inside a balloon. Leave the wires sticking outside the mouth of the balloon, and close up the mouth of the balloon with a ziptie. You can also seal up the mouth of the balloon with some grease or silicone to help seal up any leftover gaps after the ziptie is pulled tight. Then use a pin to place a small hole in the balloon where the servo output shaft is located, and pull the balloon so that the shaft slides through it. Then you can reinstall your servo horn or servo saver. Another method of protecting your servo from moisture, is to use some silicone sealant. This results in a stock-like appearance, as you can't really tell that anything has been done to the servo. Take the servo case halves apart, and apply a small bead of silicone where the they connect. Then simply reassemble the case and allow the silicone time to cure. To protect the area around the servo output shaft, use a small o-ring coated with some grease to form a seal when you install a servo horn or servo saver. Speed Controller
Protecting your speed control is a very important, yet difficult, step to undertake. I often hear of people encasing their ESC inside a balloon, but that's often a dangerous idea. It severely hampers the ESC's ability to cool itself, which could lead to the ESC overheating and damaging itself. At the very least, you might experience the balloon the ESC is encased in melting. So if you choose this method of protection, I would encourage you to frequently monitor your ESC's temperature to avoid such problems. Small plastic project boxes like they sell at radio shack can be used to seal up the ESC or ESC and Receiver too.
The only good solution for a MSC, would be to make a shield to protect the electronics from the elements. You can fabricate something out of scrap lexan, or simply carve up a 2-liter drink bottle. A few pieces of duct tape will hold the shield in place and help prevent any moisture from finding it's way inside. As a general rule, since a shield sits away from the ESC by several inches, the ESC shouldn't overheat with this method. However it would still be advisable to check it from time to time to ensure that it's still not overheating.
It's also possible to buy waterproof ESC's for use during wet and snowy conditions. MTroniks is one company that is well known for this. Also LRP makes water proof ESC's. Misc. Tips
In addition to the things listed above you can use plastidip found at local hardware stores (it's a liquid that hardens into a rubber coating) and dip your parts in it to seal them, servos are a prime cantidate for plastidip.
Put a thin coating of oil on the outer motor bearing to help prevent water intrusion.
WD-40 can be used on the motor, but use it sparingly, but spray some on a cloth and wipe down your metal chassis parts just like you'd oil a gun and the water will bead right off and it makes clean up a snap. Armorall works also, some people use armorall on the plastic parts. I use rainx on the outside of the body or wipe it with a thin coat of armorall the help make clean up easy.
Most of the info above can be found on: http://www.misbehavin-rc.com/pit-lane/wate...terproofing.asp
Except for the last few lines I give full credit to them on this article. I use alot of these tips on my Electrics and on my Nitro 4x4's also. So if there is a nitro tip mentioned please take it for what it is.
If you have other water proofing ideas please share them here.