Spur Gear Replacement Instructions

Article #35189

Spur Gear Replacement Instructions for T-Maxx™

 

Here is an example of a couple of stripped spur gears. Notice the flattened teeth, and how they are literally wiped out all the way around the gear. Once the engine has shifted over from an impact or just from loose engine screws, this can happen as soon as you pull the trigger.

There are many teeth that are chipped on these two spur gears. These were more than likely damaged from a very severe impact at a high rate of speed. it's probable that the engine mounts were broken as well.

Here is a clear cut case of a slipper clutch set very loose. If engine RPM rapidly increases and the truck speed does not, stop the truck immediately, and check the slipper clutch.

 

Properly adjusted gear mesh and slipper settings will prevent things like this from happening to your spur gear. Regular checks need to be made before, after, and even during each running session.

 


1. Remove engine screws & fuel tank

Start by removing the four 3x10CS (Cap-Screw) screws that secure the engine to the chassis. These are located under the chassis just below the engine. Note: Do not remove the engine, only the screws.

 

Remove the four 3x10CST (Countersunk Self-Tapping Screw) screws that secure the fuel tank to the chssis. Lift the fuel tank from the chassis (leaving the fuel lines attached) up and over the rear shock tower to gain access to the slipper nut.

2. Remove spur gear

Tip: apply lateral pressure to the side of the spur gear to hold the slipper shaft still while threading the slipper nut off of the shaft.

 

Remove the 4.0NL (Nylon Locknut) from the slipper shaft. Slide the slipper spring along with the pressure plate and pressure ring off of the shaft. Slide the engine over just enough to clear a path for the spur gear.

Remove just the spur gear, leaving the bronze bushing on the slipper shaft. Note: A new bronze bushing is included with the new spur gear, but it is not necessary to replace the used one as long as it is not damaged. Tip: Hold a small screwdriver against the bushing while pulling on the spur gear. The spur gear can be removed from the slipper shaft more easily without the bushing in the middle.

 

3. Install friction pegs

Transfer the six friction pegs from the old spur gear to the new spur gear. The friction pegs can easily be pushed out of the old spur gear and pushed into the holes of the new one. Make sure that all six pegs are installed, and located into every other hole.

 

Important: Do not reuse friction pegs that are excessively worn or melted. If the old friction pegs are worn down to the plastic of the spur gear, then they need to be replaced.

 

 

4. Install new spur gear

Make sure that the pressure ring and the pressure plate (currently on the slipper shaft) are keyed into each other, and fit the new spur gear (with fiction pegs) onto the bronze bushing followed by the outer pressure ring and pressure plate. Note: The notch in the pressure ring must key in with the pin in the pressure plate. Tip: You can use a small dab of CA to hold the rings on the plate.

Slide the slipper spring over the slipper shaft and secure the assembly with the 4.0NL. Tighten the slipper nut until the spring is stacked solid, then back off ¼ turn.

 

5. Reconnect fuel tank & adjust gear mesh

Reconnect the fuel tank to the chassis and secure it with the four 3x10CST screws. Thread the four 3x10CS screws back into the engine mount through the bottom of the chassis until snug, then back off slightly to adjust gear mesh.

Make sure that the engine is aligned straight on the chassis, and slide the engine (with clutch bell) toward the spur gear until the teeth from both gears are meshed together.

This pic is an example of the clutch bell gear and the spur too close together. This condition will cause binding (inefficient performance), and premature wear.

This is an example of proper gear mesh. The gears are as close together as can be without binding.

These two gears are set too far apart. This "loose" mesh will not last very long under power, and will eventually strip

 

The gears should be as close together as possible, and spin freely without binding. Tip: Push the clutch bell gear up against the spur gear just so that the gears bind a little, then back off slightly just until the gears spin freely. Tighten the four 3x10CS engine mounting screws.

Double check the gears for smooth operation. They should spin freely with no binding. This completes the spur gear replacement instructions.

Attention: Check slipper tension during first run after spur gear replacement. Listen for slipping frm the slipper clutch. If the truck revs high without picking up speed quickly, the slipper nut needs to be tightened until the slipping goes away.


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