TRX-4 79 K5 Blazer Manual
28 
•
 TRX-4
Adjusting Gear Mesh
Incorrect gear mesh is the most 
common cause of stripped spur 
gears. Your model includes a fixed 
gear positioning system to simplify 
the process and ensure proper gear 
mesh settings. Access the gears by 
removing the three 3x8mm button-
head screws from the gear cover; 
remove the gear cover. Remove the 
motor/motor plate assembly from 
the chassis.
To set the gear mesh, use the chart 
to the left to identify the screw 
positions on the motor plate (A - H) 
that correspond with the chosen 
motor pinion (9-T - 22-T) and spur gear size (39-T or 45-T). Remove 
the two screws from the motor/motor plate and reinstall in the 
corresponding positions; reinstall the motor/motor plate assembly 
in the chassis.
Motor Removal/Installation
To access the motor, remove the gear cover by removing the three 
3x8mm button-head cap screws. Remove the motor/motor plate 
assembly from the chassis; then, remove the two screws holding 
the motor to the motor plate. Installation of the motor is the 
reverse of removal.
SERVO STEERING SYSTEM
TRX-4 uses a single metal gear servo for powerful, responsive steering. 
Adjusting the Steering System
1.
 Remove the servo horn and steering links from the servo. 
2. Adjust the drag link to 133.2mm; adjust the steering link to 77.3mm.
3.  Switch on the power to the receiver and the transmitter.
4. Adjust the steering trim on the transmitter to the neutral “0” position.
5. Connect one end of a steering link to the steering servo arm and the 
other end to the servo horn.
6. Position the servo horn perpendicular to the centerline of the vehicle 
as shown below.
If you are using aftermarket servos, it is important to use servo horns 
designed for TRX-4. The servo horns must measure 22mm from the 
steering linkage mounting hole to the servo mounting hole. 
TUNING ADJUSTMENTS
Spur Gear
Pinion Gear
39 45
9
- A
10
- B
11
- C
12
- D
13
- E
14
- F
15
A G
16
B H
17
C -
18
D -
19
E -
20
F -
21
G -
22
H -
Stock factory gearing
Does not fit
Screw Positions
133.2mm
Drag Link
77.3mm
Steering Link
Front of 
Truck










