Project: Racer Slash 4×4

Project: Racer Slash 4×4

Words and Photos Drew Trudeau


There is a moment everyone has at the track when they realize that running a vehicle with its stock parts just won’t cut it. If you have invested in a high performance RC model like the Traxxas Slash 4×4, there’s an entire world open to you in the form of upgrades and hop-ups. With upgrades coming at it from all angles, choosing the right ones is a balancing act of personal finances and choosing the upgrades that immediately enhance performance. Before I start emptying the checking account on Low CG chassis kits and other stuff for my budding racer, I choose to keep it simple to start by swapping out the truck’s slipper/spur gear for Traxxas’ Center Differential upgrade. I’ll will also be upgrading the plastic spur gear for a Robinson Racing spur complimented with their line of Absolute pinion gears. Let’s get building!

All The Right Gears
To kick things off, I choose to pair the Traxxas Center Differential upgrade with a good set of gears from Robinson Racing. Robinson Racing makes spur gears specifically meant to bolt onto the Traxxas upgrade diff. If you are serious about dialing in your truck on varying track types it is definitely suggested you purchase a few different pinion gears with different tooth counts. Always get suggestions from other racers and your local hobby store or race track about what gearing ratios to start with.


Out with the Slipper
Swapping out the slipper gear in the Slash is a simple endeavor. First you will want to unscrew the four main chassis screws that hold the rear assembly to the main chassis. With the gear cover off, there are two screws on the top and two more on the bottom that you will need to remove using a 2.5mm hex driver. Once those are removed the rear assembly will slide out making the slipper gear accessible and easy to pull out.

RemovingTopChassisScrews RemovingSlipper

In with the Center Diff
Now that the slipper gear is removed you will want to mount the Robinson Racing’s spur gear onto the Traxxas Center Differential which is held in place with four screws. Traxxas has already pre-built the center differential housing using 100k weight diff fluid for use with most surface conditions. Stand the chassis up on its front end and insert the new center diff so that the splined shaft adapter is received by the center drive shaft and can rotate smoothly.


Here you can see the difference between the Robinson/Traxxas upgrade part and the stock Slash 4×4 slipper assemblies.

Rear reassembly
Now with the center differential in place slide the rear assembly back into place until the drive shaft hits the rear differential. To help the rear output shaft of the center differential lock into the key of the rear differential you will need to slowly rotate the rear tires until the shaft slides and sets into place. Once you have the center differential in place you then simply screw the chassis back into place with the original four screws. Make sure the differential is rotating freely and all four wheels rotate cleanly and smoothly.

ReplacingChassisWCenterDiff ScrewingBottomChassis

Picking the perfect pinion
Your Slash 4×4 is almost ready to hit the track again but now that you have upgraded the spur and differential it is time to consider coupling it with a high quality pinion gear to set the ratio for the track you are going to. Everyone wants their car to go fast and perform at its best and understanding gear ratios, final drive ratios and rollouts is a key to winning. You will want to explore trying out different gearings during your practice runs but always ask for advice and get suggestions from others who are familiar with the track you are going to race at. And if you are not sure what gearing to use you can always go to your vehicles stock gearing tooth count as a default starting point.


Swapping out the center slipper unit for the Traxxas center diff made a huge difference in overall performance and boy was it an easy upgrade to install. The differential’s ability to transfer power during traction loss to the front or rear tires was very evident when cornering where I really pushed the vehicle.


Having the center diff hop-up coupled with the low CG conversion kit sounds like a real one-two punch fpr making this Slash a top qualifier so I think that’s going to be next on my shopping list. The combination of fluid controlled traction and low center of gravity is sure to make our racer Slash 4×4 a true competitor. Stay tuned for more!




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Updated: July 21, 2015 — 3:51 PM
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