Low-turn motor

For rock crawling, torque is king, and one way to get that torque is by using a high-turn motor like the LRP Truck Puller II I used in my truck. The more turns it has, the stronger its magnetic field will be, and the truck will have more power. If you don’t want to spend any money, the motor that comes with the TXT-1 will work for you. But if you have a few bucks, you can pick up a lathe motor that’s designed for rock crawling. These suckers have winds in the 55-turn range—way more than any stock motor, and they aren’t too expensive.

Gear reduction

Another way to turn this truck into a torque monster is to reduce the gear ratio as much as you can. You can install a smaller pinion gear, but that takes you only so far. Your best bet is to install a gear-reduction unit. This basically adds to the number of gears in the transmission and reduces the gear ratio. You can fine-tune it by changing the size of the pinion gear that drives it and the pinion gear inside the transmission, depending on which gear reduction you use. Tamiya produced a dump truck based on the Juggernaut 2, which uses the same transmission as the TXT-1, and it came with its own gear-reduction unit. You can use this gear reduction if you can’t find another unit like the two offered by RC4WD. To make that happen, you’ll need these Tamiya parts: nos. 0225092, 9335344, 9415714.

Get a high-torque servo

Torque is important for steering, too. Buy a strong, high-torque servo for the job. Don’t install a servo-saver; it will make the steering spongy, and you need it to be as tight as possible here. You don’t have to worry about stripping a servo because the truck moves so slowly that most hits that the servo takes won’t damage it.

Lock the diff

Traction is very important for getting over rocks, and your truck’s stock diff isn’t up to the job. The stock diff will allow the tires with the least traction to spin, and if this happens, your truck won’t go very far. The front and rear tires should pull the truck equally at all times, so you have to lock the front and rear diffs. This is a simple mod. Remove the diffs from the axles, and clean all the grease off the gears. Put the gears back in the diff and coat them with an epoxy to set them in place and lock the diff. I use J-B Weld because it holds up well to abuse. Assemble the diff and turn it to coat all the gears with the epoxy before you set the diff aside to let the epoxy cure overnight. You don’t need much epoxy—just enough to coat the gears.

Ditch the lower bumpers & skidplates

The lower front bumper and skidplate do a good job of protecting the axles but will get hung up on the rocks and limit the TXT-1’s maneuverability, so we’ll have to remove them—but not entirely. You’ll need the upper mounts for your shocks and suspension links. Remove the front and rear bumpers and skidplates from the axle. Ditch the skidplates, and cut the front bumpers off at the points where they just meet the axles. You basically want to save the upper and lower mounts used for the shocks and lower links.

Shock mods

Remove the shocks, the shock mounts, the cantilevers and cantilever links, and set them aside. The shocks are what you’re after here. Now ditch the shock-shaft spacers and the springs. Removing the spacers will give the shocks more travel, and you’ll need that for better axle articulation. The stock springs are way too stiff, so replace them; softer springs are ideal here. I used a set of Losi orange springs on my truck. Losi offers springs in several rates, and they will allow you to fine-tune your suspension. Now mount your shocks directly on the axle to eliminate the cantilevers. Thread the pivot ball from the shock side of the cantilever into your chassis, as shown in the photos. You’ll mount the shock-shaft side of the shock here and screw the other end to the upper mount on the front bumper. You want to mount the shock body as low as it can go to lower the truck’s center of gravity (CG). You’ll have to cut the chassis to make room for the shock.

Remove the swaybars

The swaybars on the lower links allow you to increase or decrease the TXT-1’s axle articulation. For rock crawling, you want maximum axle articulation, so remove the front and rear bars from the links and toss them.

Lose the weight

To trim fat, I removed the front and rear bumpers. I also removed the lower front and rear cross-members for axle clearance. The middle third of the chassis also has two cross-members that hold the chassis plates together. You can remove both of them because the transmission does the same job, and removing the cross-members will give the upper links more room to move when the suspension is compressed. Remove the stock battery holder. It weighs a lot, and you won’t need it because you’ll mount the battery pack much lower on the chassis.

Reverse tires & weighted wheels

Keeping the CG as low as it can go is the key to having a crawler that handles well. An easy way to do this is to stick lead weights around the front rims. Cut off the plastic support pieces from the center along the rim’s outside diameter. Clean the rim with motor spray to remove any mold-release agent or oil from your fingers. Now wrap the stick-on lead weight around the center of the rim. Some think that for better traction, you should reverse the direction of the tire treads when you put them back on the rims. Remember to glue the tires to the front and rear rims.

Side-by-side battery pack

A truck like this doesn’t have enough room for a typical stick pack. Build a side-by-side pack to fit a lower mounting position. People usually mount them on the axles, the upper links, or the chassis. I went with the chassis. I used two of the cross-members that I had removed, drilled the chassis in a new place and mounted the pack on them. Secure the pack with Velcro or wire ties.

Steering-servo mount

You removed the lower front bumpers and skidplates, so there’s nowhere to mount the steering servo. You can easily make a mount out of carbon-fiber plate or sheet aluminum. Follow the template provided to cut your mount out. Cut out the template, glue it to your material, and follow it to drill your holes and cut the plate to the correct size. Attach the servo to its mount using screws and nuts, and you’ll be able to attach the assembly to the top of the axle using screws to hold the top cover down. Do the same at the rear. If you only plan to use 2-wheel steering, use the servo plate as a place to attach the rear links to lock the rear wheels. Removing the washers from between the hubs and axles will strengthen the rear lock because the tabs will pinch the hubs when you tighten the screws, and they won’t be able to move.

There you have it!

Now you’re armed with everything you need to know to turn your TXT-1 into a rock crawler without spending a lot of money. I took my TXT-1 to a local rock-crawling comp, and it actually did pretty well against some high-tech and high-dollar machines. This is just the beginning. You can make many other mods to take it to another level, but that’s another article. As you run your truck, you’ll probably make further tweaks, and before you know it, you’ll have a new truck. Enjoy!