Traxxas 1/16 Summit VXL 72074 Owner'S Manual Download Page 23

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1/16 SUMMIT VXL • 23

TUNING ADJUSTMENTS

wheels. Your model will generally benefit from higher viscosity oil
when climbing, rock crawling, or racing on low-traction surfaces.

From the factory, both the differentials are filled with SAE
30,000W viscosity silicone oil. This fluid gives the 1/16 Summit VXL
versatile multi-terrain handling and allows forgiving cornering
on pavement and other high-grip surfaces. For extreme off-
road terrain, the differentials may be filled with thicker fluid to
increase traction, at the expense of high-speed cornering stability.
100,000W fluid is a good starting point for extreme-terrain use;
500,000W fluid will virtually lock the differentials. The differentials
must be removed from the vehicle and disassembled to change/
replace oil. Only use silicone oil in the differentials. Traxxas sells a
variety of oil viscosities (see your parts list).

Note:

Heavier oil will

allow power to be transferred even with one or more tires off the
ground. This can make the vehicle more likely to overturn.

MOTOR AND GEARING

Extensive testing has been done to determine the best gear ratio
for your model. The stock gearing balances power, speed, and
efficiency to optimize the performance of the model. However,
you may wish to try different gear ratios in order to customize the
performance of your model. The gearing chart on this page shows
appropriate gearing for the model.

By installing a pinion with fewer teeth, or a spur gear with
more teeth, the transmission’s final drive ratio is increased.
This means greater rpm is required to achieve a given speed.
Using a numerically higher gear ratio will increase torque, but
reduce top speed. Installing a pinion with more teeth, or a spur
gear with fewer teeth, will decrease the final drive ratio, which
will generally increase top speed but reduce torque. However,
installing too large a pinion will “overgear” the model, which will
reduce performance and may overheat the motor and speed
control. Use the following formula to calculate the overall ratio for
combinations not listed on the gear chart:

Motor Installation

To access the motor,
remove the gear
cover by removing
the single screw
on the top of the
gear cover. The
motor uses an
aluminum mount
for quick, easy motor access and gearing
adjustment. To remove the motor, first
open the right battery door and slide out
the ESC. Next, remove the single large hex
screw using the supplied 2.5mm wrench.
Then rotate the motor and mount to the
side of the model, and slide backward off
the post.

The motor mount was carefully
engineered to provide additional features
and adjustability. Two sets of holes
are provided for use with brushed and
brushless motors. The holes for brushed motors are spaced 16mm
apart and accept 2.5mm screws. The holes for brushless motors are
spaced 19mm apart and accept 3mm screws.

Pinion Gear Installation Instructions

1. Remove the motor as described

in Motor Installation.

2. Use a1.5mm wrench to loosen the

pinion’s set screw. Remove the pinion.

3. Place the replacement pinion gear onto

the motor shaft. Align the set screw hole
with the flat side of the shaft.

4. Thread a 1.5mm set screw into the

pinion gear but do not tighten it yet.

5. Slide the pinion gear down the motor shaft so the wrench shaft

fits into the notch in the motor mount, as shown. Tighten the
set screw.

# Spur Gear Teeth

x 5.04 = Final Gear Ratio

# Pinion Gear Teeth

Brushed Motors

Brushless Motors

Motor Mount Positions

Gearing Compatibility Chart

This chart shows a full range of gear
combinations. The gear combinations
in gray are not suitable when using the
included 6-cell battery, speed control,
and motor. These gear combinations
have been included in this chart as
they may be used with certain other
aftermarket equipment combinations.

Spur Gear

Pinion Gear

25.20

23.10

21.32

19.80

18.48

15.75

17.33

14.82

16.31

14.00