How to Upgrade Driveshafts and Outdrive Cups on Your RC Monster Truck

If you push your RC monster truck hard, the drivetrain takes a beating. Driveshafts and outdrive cups are two of the most stressed parts, and upgrading them can save you from mid-run breakdowns. In this guide, we'll walk you through when to upgrade, what to look for, and how to install new parts safely.

Even if you're new to wrenching on RC cars, this is a manageable project with the right tools and a little patience. We'll cover the basics, from recognizing wear to choosing the right metal upgrades, so you can keep your truck running strong.

Why Upgrade Driveshafts and Outdrive Cups?

Stock plastic driveshafts and outdrive cups are designed to be lightweight and cheap, but they wear out quickly under high torque or rough terrain. Symptoms like clicking noises, vibration, or loss of power often point to worn cups or bent shafts. Upgrading to metal parts, such as the RCG Racing MT-One Metal Front CAD Shafts & Pins & Lock Nut M4 (Upgrade), improves durability and reduces flex, giving you more consistent power delivery.

Outdrive cups are the small yokes that connect the driveshaft to the differential or transmission. Over time, the pin holes can oval out, causing slop and premature wear on the pins. Replacing them before they fail prevents damage to the transmission case and other drivetrain components. For popular models like the RCG Racing MT-One 1/16 Monster Truck, metal cups are a direct fit and a worthwhile investment.

• Listen for clicking or grinding—early signs of worn cups or shafts.
• Check for play in the drivetrain by gently twisting the wheels back and forth.

Tools and Parts You'll Need

Before starting, gather the right tools: a set of hex drivers (metric sizes like 1.5mm, 2.0mm, and 2.5mm are common), a small Phillips screwdriver, needle-nose pliers, and a workbench with good lighting. You may also need threadlocker (blue Loctite) to keep screws from vibrating loose, and a clean cloth to wipe off old grease.

When selecting replacement parts, check your truck's manual for the correct size and spline count. For example, the RCG Racing 10-Series 1/10 Rear Cups are designed for 1/10 scale vehicles, while the MT-One uses different parts. Always confirm compatibility with your specific model before ordering. If you're unsure, contact the store or check online forums for advice.

• Use threadlocker on metal-to-metal screws—it prevents loosening from vibration.
• Keep a parts tray or small containers to avoid losing pins and screws.

Step-by-Step Installation Guide

Step 1: Remove the wheels and any body panels that block access to the drivetrain. On many trucks, you'll need to remove the skid plate or lower chassis brace to reach the driveshaft. Keep track of which screws go where—using a labeled container helps.

Step 2: Disconnect the driveshaft from the differential and transmission outdrive cups. Depending on your truck, you may need to remove a small pin or clip. Use pliers to pull the pin out carefully, and slide the shaft out of the cup. If the shaft is stuck, gently tap it with a plastic hammer to avoid damaging the threads.

Step 3: Install the new outdrive cups first. Slide them onto the differential or transmission output, and secure them with the provided screws or pins. Apply a drop of threadlocker to the screws and tighten them to the recommended torque (usually snug, not over-tightened).

Step 4: Attach the new driveshaft. Align the pin holes and insert the pins, then secure with clips or screws. Make sure the shaft rotates freely without binding. Finally, reinstall the wheels and body, and give the truck a test run on a flat surface to check for smooth operation.

• If your truck uses grub screws, clean the threads with brake cleaner before applying threadlocker.
• Test the drivetrain by hand before running under power—any binding will cause heat and wear.

Maintenance Tips to Extend Drivetrain Life

After upgrading, regular maintenance keeps your drivetrain running smoothly. After every few runs, inspect the driveshafts and outdrive cups for signs of wear, such as shiny spots or elongated holes. Clean off dirt and debris with a brush, and re-grease the cups and pins with a light lithium grease.

Also, check the screws and pins for tightness. The constant flexing of the drivetrain can loosen them over time. A quick once-over before each session prevents unexpected failures. If you notice unusual noise or vibration, stop and investigate—catching a problem early saves you from replacing more expensive parts like the differential or transmission.

• Store your truck with the wheels off the ground to relieve pressure on the drivetrain.
• Use a silicone spray on moving parts after cleaning to keep them lubricated.

Upgrading driveshafts and outdrive cups is one of the most effective ways to boost the reliability of your RC monster truck. With the right parts and a little patience, you can tackle this project in an afternoon and enjoy more worry-free running. For popular models like the RCG Racing MT-One, metal upgrades are a smart investment that pays off in durability.