Traxxas Ultra Shocks are designed for years of rugged, dependable service. But certain parts can wear out over time. Check the shocks periodically for signs of wear. Leaking oil, caked on dirt, or a bent shaft are signs that the shock needs to be rebuilt.
If the shock does not compress and rebound smoothly or rebounds quickly without any resistance, this is also an indicator that the shocks need some attention. Shocks come in different sizes and colors, so find your model on Traxxas.com and look under ‘Accessories’ to find the appropriate parts for repairing or rebuilding your Ultra Shocks.
Check the links in the description to find parts for specific Traxxas models. Pre-built Ultra Shocks are available for some models. Ideally, all shocks should be rebuilt at the same time to ensure even handling and optimal performance.
For this demonstration, we will rebuild the shocks on this Slash with new seals, pistons, and shock oil. Tools needed will include side cutters or needle nose pliers, a small flat-head screwdriver, the 4-way wrench from your accessory kit, and a Philips head screwdriver or appropriate hex tool to remove the shocks from the vehicle. An empty water bottle or cup, and microfiber cloth or paper towels will also be useful for cleanup and disposing old shock oil.
Shock oil is available in various weights to affect rebound and compression.
We will use the standard 30 weight oil. First, remove the shock from the vehicle.
Remove the wheel if necessary for easier access. Some models have a small washer behind the top of the shocks.
Be careful not to lose this washer, and put it back in place when replacing the shocks. Remove the lower spring retainer, then remove the spring and upper retainer. Clean off any excess dirt and oil remove the shock cap by unscrewing it, using a tool if necessary. Drain the old shock oil into an empty water bottle or cup and discard.
Remove the old diaphragm.
Use the side cutters to firmly hold the shock shaft, getting them as close to the rod as possible. Remove the rod end from the shaft by turning it counterclockwise.
Now you can push the shock shaft up and out of the body. Set aside the shaft and remove the lower cap from the shock body.
Underneath the lower cap you’ll find two seals with a plastic spacer in between them.
Use a small flat-head screwdriver to remove these parts and replace them with the new o-rings and spacer. Lubricate the new seals with a drop of silicone shock oil.
Now replace the lower cap. Remove the clip from the shaft if replacing the piston. To do this remove the old piston and replace with a new one, ensuring that the rounded end is pointed down. Now we will begin to re-assemble the shock. Lubricate the shaft with a drop of shock oil and gently put it through the shock body.
Hold the shock shaft firmly with the side cutters and screw on the rod end. With the shaft all the way down, slowly fill the shock body with oil and let it run down the inside of the body until it is just below the top of the body. Slowly push the shaft up about halfway and back down to remove any air bubbles.
You may need to repeat this process a few times until all the bubbles are gone. Make sure the piston stays submerged in oil or new bubbles may form. Let the shock sit upright for a few minutes until all the air escapes. Top off the shock oil and put on a new diaphragm.
The shock doesn’t need to be filled to the top. Leave about a millimeter for the diaphragm. Any excess oil should drain out when the diaphragm is put in place. Re-install the shock cap and tighten it to avoid any leaking. Move the shaft in and out vigorously, and listen for any air bubbles in the oil.
A properly filled shock should be almost silent when compressed. If you hear any bubbles, remove the cap again and let the shock sit until all the air has escaped. When properly filled the shock shaft should rebound about one third to one half of the way on its own.
If the shock does not compress it may be overfilled. If this happens, remove the cap and let out small amounts of oil as needed. Replace the spring and retainers and mount the shock back onto the vehicle. Now you’re shocks are as good as new.
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