38 • SLAYER PRO 4X4
ADVANCED TUNING ADJUSTMENTS
TRANSMISSION AND DIFFERENTIAL TUNING
Adjusting the Gear Ratio
The gear ratio on Slayer Pro 4x4 can be adjusted for different
conditions that may require either increased acceleration or increased
top speed. Adjusting the gear ratio is accomplished by changing the
clutch bell on the engine and/or the spur gear (slipper clutch gear) on
the transmission. From the factory, Slayer Pro 4x4 is equipped with a
15-tooth clutch bell and a 36-tooth spur gear. This combination will
provide a good balance of acceleration and top speed. Optional spur
gears and clutch bell gears are listed on your parts list. Refer to the
sidebar chart for possible gearing combinations.
Adjusting the Two-Speed Ratios
Slayer Pro 4x4 is equipped to allow adjustment to the two-speed
by installing optional close and wide-ratio gearsets. This requires
transmission removal and disassembly (see Traxxas.com for detailed
instructions). The close ratio gearsets will reduce top speed slightly
but will provide more powerful acceleration by reducing engine rpm
loss when shifting from 1st gear to 2nd gear. The wide ratio gear set is
installed in the Slayer Pro 4x4. The additional horsepower and torque
output of the TRX 3.3 engine provides seamless shifting even with the
larger gap between first and second gears.
Tuning The Sealed Gear Differentials
Slayer Pro 4x4’s front and rear gear differentials allow the left and right
wheels to spin at different speeds while turning so that the tires do
not scuff or skid. This decreases the turning radius and increases
steering performance.
The performance of the differentials can be tuned for different driving
conditions and performance requirements. The differentials are filled
with silicone differential fluid, and are sealed to maintain consistent
long-term performance. Changing the oil in the differential with either
lower or higher viscosity oil will vary the performance characteristics
of the differentials. Changing to a higher viscosity oil in the differential
will reduce the tendency for engine power to be transferred to the
wheel with the least traction. You may notice this when making sharp
turns on slick surfaces. The unloaded wheels on the inside of the turn
have the least traction and tend to spin up to extremely high rpms.
Higher viscosity (thicker) oil causes the differential to act like a limited-
slip differential, distributing more equal power to the left and right
wheels. Slayer Pro 4x4 will generally benefit from higher viscosity oil
when climbing, rock crawling, or racing on low traction surfaces.
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.
From the factory, both the differentials are filled with SAE 30,000W
viscosity silicone oil. Only use silicone oil in the differentials. Traxxas
sells SAE 10,000W and SAE 50,000W viscosity oil (see your parts
list). The differentials have to be removed from the vehicle and
disassembled to change/replace oil.
SHOCK TUNING
Shock Pistons
The shock pistons can be replaced
with the available optional pistons to
vary the amount of damping. Optional
pistons with bypass holes that are
smaller (#2 or #3) than the factory
installed stock pistons can be used to
increase damping. From the factory,
Slayer Pro 4x4 is equipped with #1
pistons in the front and rear.
Shock disassembly
The shocks must be removed from the
vehicle and disassembled to change
the pistons. Use the shock exploded
views included with the model to aid
in the assembly process.
1. Remove the spring and lower
spring retainer from the shock.
2. Remove the shock cap (A) and
empty the shock body of shock oil.
3. Remove the lower cap (B) and the
X-ring from the shock body.
4. Use side cutters to grip the shock
shaft just above the rod end (C).
Remove the rod end from the
shock shaft using the suspension
multi tool (C).
5. Remove the shock shaft with piston from the shock body out
through the top of the shock body.
A. Tighten/Loosen Upper Cap
C. Remove/Install Rod End
B. Tighten/Loosen Lower Cap
Multi-tool Shock Functions
Never slide the threads on
the shock rod past the X-ring
seal when it is installed and
compressed by the bottom
cap of the shock. Doing so will
damage the seal and cause
shock oil to leak.
Use higher viscosity
(thicker) diff oil for:
• More power to the wheels
with the most traction.
• Racing on low-traction
smooth surfaces.
• Better performance for
climbing on uneven terrain.
Using lower viscosity
(thinner) diff oil for:
• More power to the wheels
with least traction.
• Racing on low-traction
rough surfaces.
