Transmission and Differential tuning
Adjusting the Gear Ratio
The gear ratio on Jato can be adjusted for different conditions that may
require increased acceleration. 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, Jato is equipped with a
24-tooth clutch bell and a 54-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 chart for
possible gearing combinations.
The following gear ratio chart shows the available combinations with
optional spur gears, clutch bells, and two-speed gear sets.
Tuning The Sealed Gear Differential
Jato’s rear gear differential allows the left and right wheels to spin at
different speeds while turning so the tires do not scuff or skid.
This decreases the turning radius and increases steering performance.
The performance of the differential can be tuned for different driving
conditions and performance requirements. The differential is filled with
silicone differential fluid, and is 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
differential. The differential uses standard silicone shock oils.
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. Jato will generally benefit from higher
viscosity oil when racing on low traction surfaces.
From the factory, the differential is filled with 10K weight diff oil. Use only
silicone oil in the differential. The differential has to be removed from the
vehicle and disassembled to change/replace oil.
Removing the Rear Differential
1.
Remove the four 2.5x10-caphead screws from the rear battery box,
and remove the battery cover.
2.
Remove the two 3x15 countersunk screws and the bottom rear of the
chassis. Remove the two 3x10-buttonhead screws that secure the
battery box to the transmission housing. Pull the battery box along
with the differential cover away from the transmission housing.
3.
Remove the 2.5x12-screwpin from each output yoke, and slide the
output yokes off of the output shafts.
4.
Remove the differential from the rear of the transmission housing.
Refer to your Jato exploded view parts diagrams for more detail.
44 • Jato 3.3
Advanced Tuning Adjustments
Clutch Bell
16
18
20
22
24
Gear
1st
2nd
1st
2nd
1st
2nd
1st
2nd
1st
2nd
54
-
-
13.03
9.72
11.73
8.75
10.66
7.96
9.77*
7.29*
56
15.20
11.34
13.51
10.08
12.16
9.08
11.05
8.25
10.13
7.56
# of Spur Gear Teeth
58
15.74
11.75
13.99
10.44
12.59
9.40
11.45
8.54
-
-
*stock configuration out of the box
Differential Tuning:
Use higher viscosity
(thicker) 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) oil for:
More power to the wheels
with least traction.
Racing on low-traction
rough surfaces.
