One of the best ways to get instant rock crawling performance out of your truck is to lock your differential. The differential is a device built into your truck’s gearbox that allows the wheels to turn at different speeds when you go around a corner. Its purpose is to allow the vehicle to make tighter turns with less strain on the drivetrain. Although the diff is great for road cars it’s very detrimental in offroad situations. That’s because when you’re climbing one wheel is likely to lose traction and in that situation the differential transfers all of its power from the wheel that has grip to the one that is slipping; basically stopping the vehicle in it’s tracks. This is where locking the diff comes into play. By locking both sides of the diff together you force both wheels to turn at the same speed at all times. This increases your truck’s climbing ability by a ton!
asd The obvious first step is to remove the gearbox/axle from your truck. We won’t go into much detail on this because that will vary greatly depending on your truck. We suggest you look into your vehicle’s manual for specifics. The truck we’re doing this project on is a Tamiya Clod Buster. The Clod Buster, like many r/c trucks, has an axle (and diff) in both the front and the back. A great starting point is to lock the rear differential first, and take it for a test drive. Then if you like the results you can go a step further and lock the front too.
Next thing to do is disassemble the axle. Again no sense getting into minute details because this will vary from truck to truck. On the Clod Buster it’s just a matter of removing two screws holding the motor in place and then the six holding the two gear cases together. Just be observant of which screws go where as they can be different sizes and lengths.
Here is the part you’ve been waiting for, how to lock the diff. First we should get into what you are going to use to lock the diff. Some people will recommend using a product called JB Weld which is basically a thick epoxy glue. This works perfectly but because JB Weld cures to a rock solid lump it’s impossible to remove once in place. That’s fine if you intend to leave the diff locked for eternity, but if you think you may change your mind it’s best to go another route. Another method of locking diffs that I’ve heard people recommend is filling the diff with Silly Putty. Personally I haven’t tried it but I have my doubts about how well it would stay in a non sealed diff like that in the ClodBuster. The best method I’ve found to lock the diff is by gluing it with hot glue. Not only is it really strong but it’s also removable. If you ever get tired of your differential(s) being lock all you need to do is peel the hot glue off!
To actually lock the diff with hot glue is rather simple. Just lay the main gear section of the diff on a flat surface and put a lot of hot glue in between the smaller gears (known as spider gears). Then before the glue cools place the side spider gear in place and hold it until the glue dries. After you’ve done one side flip the gear over and do the same on the other side. The arrows in the picture below show the general area of where to place the glue.
The picture below depicts the gear type differential that was in our Clod. However you may find a ball differential in your truck. We have not tested the method below on a ball diff but it should work just as well. However a very common method of locking a ball diff is by removing the balls completely. Just disassemble it, remove the balls, and reassemble it.
Here are two pictures of the diff locked. After the glue has dried (cooled) I’d suggest removing any hot glue “hair” that you can see. That’s it! Time to reassemble everything and hit the rocks!