Slash 4X4 Differential and Clutch Upgrade
Upgrade Your Slash® 4X4 Drivetrain for Maximum Strength and Durability!
The Traxxas Slash 4X4 is one of the most versatile platforms available today with a nearly limitless supply of upgrades. This article focuses on the drivetrain and how to beef it up for some serious power upgrades down the road. If you haven’t already done so, consider adding the bulletproof 6 mm axles from the XO-1®. You can see how it's done in one of our earlier articles on upgrading the driveshaft on Traxxas 4x4 models.
This article demonstrates how to install reinforced differentials from the XO-1 into the Slash along with the new spiral-cut machined steel ring and pinion gears. We’ll also add the heavy-duty clutch pack, aluminum bearing adapter, and try out Traxxas’ tool kit to see how it handles some hardcore wrenching.
Apply differential oil to the X-ringsApply a small amount of differential oil onto the output shaft followed by the PTFE washer and blue X-ring before inserting it into the carrier. This will help prevent the X-ring from tearing during the assembly process and provide a good seal. Insert the shaft through the carrier and then fill the carrier approximately one-quarter full of differential oil.
Assemble the internal differential gearsNotice that the upgraded XO-1 internal differential gears feature a large steel brace for extra support. The brace only fits in one way so it’s best to do a test fitting before final assembly. Apply oil to all of the internal parts as you assemble them. This helps lubricate them, but also makes assembly easier if they all stick together.
Fill the differential carrier with oilPress the completed gear assembly down into the carrier and turn the output shaft. This will coat the gears in the differential oil at the bottom of the carrier. If necessary, add a little more oil to the carrier, but do not overfill it. Overfilling the differential can cause the seal to fail when you tighten down the ring gear. Apply oil to the second output shaft and X-ring using the same technique as before and insert it through the spiral-cut ring gear.
Attach the ring gearLine up the holes in the black rubber differential seal with the screw holes in the carrier. The holes are not pre-threaded so you’ll need to add a little pressure to get the screws started. Use the 2 mm bit from the Traxxas tool kit and tighten down the ring gear onto the carrier using an "X" pattern. The handle on the driver uses a one-way mechanism to make tightening the screws easy without having to let go.
Assemble the second differentialAssemble the second differential the same way as the first. This one should only take half as much time now that you’re familiar with the process. Take a moment to inspect the gears and wipe off any differential oil that may have leaked out. Notice how the teeth are spiral-cut. This provides a larger surface area for greater durability and power handling.
Remove the bulkheadNow that your differentials are ready to install, it’s time to remove the old ones. The Slash’s modular chassis makes this easy and straight forward. Begin by removing the four screws that hold the rear bulkhead. You'll need the 2.5 mm bit from the tool kit. Once those are out, you can remove the entire bulkhead assembly.
Remove the bumperWith the bulkhead out, it's time to remove the rear bumper. There are five screws securing the bumper to the bulkhead. Use the 2 mm bit from the tool kit to remove them.
Detach the axlesWith the bumper off, remove the two grub screws holding the axle onto the differential output shafts. You'll need the 1.5 mm bit from the tool kit. It is not absolutely necessary to remove the stainless pins holding the suspension arms to the bulkhead, but you may find that it gives you more room to work.
Remove the differential coverYou're in the home stretch now! Remove the two screws securing the differential cover and set it aside. This will give you access to the differential carrier.
Install the pinion gearNOW STOP! Before you remove the differential, take note on which side the ring gear sits. It must go back in the same way or you can lock up the entire drivetrain. Remove the old differential carrier from the bulkhead. If the bearings are in good condition, reinstall them onto the new differential. Tap the old pinion gear out of the bearing holding it in the bulkhead and install the new one.
Grease the gearsOnce you install the new differential, it's time to grease everything up. Don't go crazy with the grease, but give everything a good coating. Reinstall the differential cover when you've finished and then reattach the bumper to the bulkhead.
Remove the clutch assemblyNow that the rear differential is complete, it's time to upgrade the clutch. The heavy-duty clutch features aluminum pads for greater heat tolerance and a much larger pressure plate to handle massive power upgrades. The old clutch assembly should pull straight out of the chassis.
Use the second holeRemove the drive hub from the clutch shaft and then use the 8mm wrench to remove the locknut. This will release all the parts on the clutch shaft. Remove all the old parts and install the pin in the second hole of the clutch shaft. Slide the new pressure plate over the pin to lock it into place.
Install the bearing adapterInstall the new clutch disc onto the pressure plate. If your spur gear is in good condition remove it and attach it to the new clutch plate with the same three screws. Install the three aluminum pads onto the plate with the rounded edges facing away from the spur gear and then carefully press the clutch halves together. Slide the new aluminum bearing adapter and bearing onto the shaft with the tapered end facing the gear.
Tighten the clutchReinstall the spring onto the shaft and then the locking nut. Hold the clutch assembly together as you tighten down the nut. Tighten the nut until you compress the spring fully and then loosen the nut about half a turn.
Reinstall the clutchReinstall the drive hub onto the end of the clutch shaft and insert it back into the chassis. You may need to rotate it slightly to align it with the center driveshaft. Once it's installed, reinstall the rear bulkhead and tighten everything down.
Remove the drive hubReplacing the front differential is the same procedure as the rear with a couple extra screws. You'll need to remove the screw holding the steering arm to the bell crank to remove the front bulkhead. You also need to remove the grub screw holding the drive hub onto the pinion gear. Replace the front differential and reassemble the front bulkhead. Double-check your work and tighten everything down.
In this article we will be using 30k weight differential oil, but you may use any weight you choose. The higher the weight, the more locking action your differentials will have. This will also be a good time to inspect your Slash for damaged or worn parts. The Slash is a high performance truck and its drivetrain parts are subjected to constant punishment. It’s better to replace a worn part now than to have it fail out in the field.
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The Build
Apply differential oil to the X-ringsAssemble the internal differential gearsFill the differential carrier with oilAttach the ring gearAssemble the second differentialRemove the bulkheadRemove the bumper
Detach the axlesRemove the differential coverInstall the pinion gearGrease the gearsRemove the clutch assemblyUse the second holeInstall the bearing adapterTighten the clutchReinstall the clutchRemove the drive hubWith these drivetrain upgrades in place, your Slash 4X4 is ready to handle some serious power. Check out our parts finder for dozens of other upgrades and accessories. With the best customer service and parts support in the industry, Traxxas makes customization fun and easy for hobbyists of all skill levels.
