Traxxas Reverse installation kit, T-Maxx User guide

4907, 4908 T-Maxx 3.3 Forward/Reverse Kit Instructions

Important Note: This kit does NOT include the OptiDrive system. The truck must
come to a complete stop before shifting gears. See below for shifting instructions and
information about OptiDrive.

Tools Needed:

• 1.5mm hex wrench

• 2.0mm hex wrench

• 2.5mm hex wrench

• Needle-nose pliers

• Small flat-blade screwdriver

Transmission Removal

1. Remove the air filter from the
carburetor, and then remove the
throttle return spring from the
transmission case with a pair of
needle-nose pliers (1A).

2. Loosen the set screw at the top of
the brake cam to release the brake
arm. Pull the arm from the brake cam (1B).

3. Flip the truck over and remove the four 3x8mm
countersunk screws that attach the center skid
plate to the chassis braces (1C).

4. Remove the screw pin from the rear transmission
output yoke, and then pull the
yoke off of the shaft, leaving the
drive shaft assembly intact (1D).

5. Next, remove the seven 3x15mm
cap-head screws that secure the
transmission case to the chassis,
and then flip the truck back over
onto its wheels (1E).

6. Detach the throttle linkage
ball cup from the throttle arm
on the carburetor, and then
swing the throttle bell crank
around to where the long
throttle rod provides enough
space to pull the transmission
out of the chassis (1F). The
transmission should pull straight out of the chassis with the front drive shaft
half still attached.

7. Remove this drive shaft half by removing the setscrew pin from the output yoke (1G).

Forward / Reverse Gear Installation

1. Remove the seven 3x12
countersunk screws (2A) from the
transmission and separate the
transmission halves (2B).

2. Remove the forward-only gear
shaft assembly, along with the
brake disc, from the transmission (2C),
and then pull the blue rubber plug
from the front transmission half (2D).

3. Next, place the steel primary
gear into the front
transmission half,
followed by the disk
spring (see image 2E for
correct orientation).

4. Slide the steel reverse
idler gear (with bearing)
over the molded plastic post next to the
steel primary gear (2F), followed by the
plastic idler shaft support (2G).

5. Locate the two black forward and
reverse gears and the two metal needle
roller bearings. Press a roller bearing
assembly into each gear, with the integral
marking facing out and away from the gears (2H). Be sure to press the bearing
assemblies all the way into each gear until it bottoms out inside the gear (2I).

2E 2F

1A

1D 1E

1F

2A

2H

1B

1C

1G

2B

2C 2D

2G

2I

2J

6. Locate the forward/reverse output shaft, dog slider, four 6x8 PTFE washers, and
the two black forward/reverse gears with installed roller bearing assemblies.
Install these items onto the output shaft using image 2J for correct sequence
and orientation. Note: The forward/reverse gears must be installed onto the
output shaft with the integral markings of the roller bearings facing toward the
center of the shaft (2J).

7. Next, locate the shift fork and shaft assembly. Position the
shift fork inside and around the groove of the plastic dog
slider on the output shaft (2K). Note: The shift fork shaft
must face toward the black reverse gear (thin gear).

2K

8. Insert the entire assembly into the front transmission
half (2L). The output shaft is located through the 6x12mm
bearing at the bottom of the case, and the shift fork shaft
should slide through the same hole where the blue rubber
plug was removed (2M). Remember to position the front
brake disc between the brake calipers before sliding the
output shaft all the way into the transmission case.

9. Remove the forward-only primary gear from the
two-speed shaft by removing the primary pin retainer clip
from the gear to access the cross pin (2N). Push the pin
out of the gear and slide the gear off of the shaft.

10. Replace the gear with the included forward/reverse
primary gear in the same orientation and secure the gear
with the pin and retaining clip (2O).

11. Next, carefully join the two transmission halves together
and secure them with the seven
3x12mm countersunk screws (2P).
Reattach the front drive shaft
half to the output shaft of the
transmission and secure it with the
same screw pin (2Q).

12. Reinstall the transmission to the
chassis in the reverse order of how
it was removed. Remember to
rejoin the front drive shaft halves
together before securing the
transmission case to the chassis.

13. Reattach the throttle ball cup to
the carburetor, and then reconnect
the throttle return spring to the
transmission case. Secure the
brake arm back into the brake cam, and then reattach the air filter assembly
back onto the carburetor and secure it with the wire clip.

Channel 3 (CH3) / Shift Servo Installation

1. Locate the included #2060 shift servo and
adapter plate assembly and the four included
3x8mm button-head screws (3A).

2. Loosen the two front screws that fasten
the steering servo to the servo mount
approximately halfway. Remove the 3x8mm
button-head screw that secures the front
steering servo mount to the chassis (3B).

3. Slide the shift servo wire under the steering servo
mount and between the chassis, and then press the
wire into the cutout molded into the mount (see 3C).
After the wire is safely contained inside of the cutout,
secure the servo mount back to the chassis with the
removed 3x8mm button-head screw, then tighten the
front steering servo screws.

4. Secure the shift servo and adapter assembly to the
servo mount next to the steering servo using the
included four 3x8mm button-head screws. Note that
the adapter needs to be mounted so that the servo
is in an elevated position (see image 3D for correct
orientation).

5. Route the #2060 servo wire around the front of
the throttle servo mount toward the radio box.
Open the radio box, and then insert the shift
servo plug into the CH3-port of the receiver
(3E). Close the receiver box.

6. Locate the shift linkage wire
with the installed plastic ball
cup at one end. Insert the bare
bent end through the hole of
the shift fork shaft (from the
transmission; see image 3F),
and then connect the ball cup to the pivot
ball on the servo horn.

7. Turn on the transmitter and the model.
Press down on the red forward/reverse
switch (3G). The shift servo horn should
swing clockwise, pushing the shift fork
shaft into the transmission (forward)(3H).

8. Press the red forward/reverse switch back
up (3I), and the servo horn should swing
counterclockwise, pulling the shift fork
shaft out of the transmission (reverse)(3J).
Important: If the shift servo horn swings in
the opposite direction than described above,
then switch the CH3 servo reverse switch on
the transmitter to the opposite position and
refer to Centering the Shift Servo.

Ensuring proper installation and engagement:

1. Shift to reverse gear on the transmitter.
Roll the truck a few inches so that the shift mechanism can fully engage.

2. Check the “pre-load” on the shift spring. You should feel a light resistance on
the servo horn.

2N

2P 2Q

3E

3G

3H

Covers Part #4995X

2L

2M

2O

3A

Front of Truck

3B

3X8mm

Loosen

3C

3D

3F

3I

3J

Traxxas, 1100 Klein Road, Plano, TX 75074,

TRAXXAS.com

Phone: [phone], Fax: [phone], e-mail: [e-mail]

KC1154-R02 121218

3. Shift to forward gear on the transmitter. Again, roll the truck a few inches to
fully engage the shift mechanism in the transmission.

4. Check the “pre-load” on the shift spring. It should be about the same as it was
in second gear (but in the other direction).

5. If the spring pre-load does not feel similar in forward and reverse gear, remove
the servo horn and reinstall. Start with Step I of Centering the Shift Servo, and
make the following adjustment:
a. If the spring was tight in reverse gear, but loose in forward gear, install the

notched servo saver sleeve one tooth clockwise from the original position
(see Step II of Centering the Shift Servo).

b. If the spring was tight in forward gear, but loose in reverse gear, install the

notched servo saver sleeve one position counterclockwise from the original
position (see Step II of Centering the Shift Servo).

Forward/Reverse Shifting Tips

• This kit does not include the OptiDrive module. The truck must come to a

complete stop before shifting.

• After the truck has come to a complete stop, press the red forward/reverse switch

up to actuate Reverse or press down to actuate Forward.

• After shifting, allow the truck to roll slightly to ensure positive engagement of the

transmission. Once the truck lurches forward or back, it is then ok to apply throttle.

CAUTION: Do not switch gears at high speeds. This can cause serious damage to
the transmission gears.

OptiDrive System (optional)

The Traxxas OptiDrive electronic shift module uses advanced microprocessor
control to sense vehicle speed and optimize forward and reverse shifting. OptiDrive
also includes low battery voltage protection. These parts are needed for installing
the OptiDrive system into the 4908 T-Maxx:

• #5398 - OptiDrive shift module

• #5397 - OptiDrive sensor assembly

Centering the Shift Servo

The shift servo has been correctly centered from the
factory. The following instructions have been included

1X

for your reference.

I. Remove the 3x10mm button-head screw from the

shift servo horn, and then remove the spring, servo
horn, and the notched sleeve from the servo (1X).

II. Turn on the transmitter and the ON/

OFF switch on the model. Make sure

2X

3X

that the red forward/reverse switch on
the transmitter is positioned in the UP
(reverse) position (2X). Install the sleeve
back onto the splined output shaft of
the servo with the notch in the “12
o’clock” position (3X), and
then turn the radio system

4X

5X

and truck off.

III. Set the servo horn back

on top of the adapter as
shown (4X), and then place
the spring onto the servo
horn. Make sure to put the bottom end of the wire

6X

into the single hole (not the slot) located in the servo
horn (5X).

IV. Secure the assembly to the servo with the same

3x10mm button-head screw (6X).

4967
2743
3x4 GS

5157

5394X

5397
3215

2.5x6 CS

5396X

4967

5116
5x11 BB

2552
3x12 CCS

5365

4978
3x21 Shoulder BCS

5384 (wide)
5385 Opt. (standard)
5383 Opt. (close)

5117
6x12 BB

*

5365

Completed Installation

5393
Primary shaft

5119
10X15 BB

5183
(includes bearing)

3982
6x8x0.5 PTW

5181

5364
5364X

5393
1985

5385
M3/13.75
(screw pin)

*

5117
6x12 BB

5390

5386
3982
6x8x0.5 PTW

5390

5384 (wide)
5385 Opt. (standard)
5383 Opt. (close)

5116
5x11 BB

5183

3982
6x8x0.5 PTW

5395

5393

5390

5395

5121
6X10 NRB
(Text on bearing
towards shaft.)

5x8x0.5 PTW

5116
5x11 BB

5389X

5393

5116
5x11 BB

3982
6x8x0.5 PTW

5369
Output shaft

5366

5352

5181

5395

5121
6X10 NRB
(Text on bearing
towards shaft.)

5181

4927X

5117
6x12 BB

3982
6x8x0.5 PTW

If you have questions or need technical assistance, call Traxxas at

1-888-TRAXXAS

(1-888-872-9927) (U.S. residents only)

*Apply a light coating of automotive wheel bearing grease to these gears.

4927X
M4/14.5

5352X

5352X

5351

Shift Servo Assembly

4995X
2576
3X8 BCS

FRONT

3956 54T
3957 56T Opt.
3958 58T Opt.

5352X

5366

5116

5x11 BB

4995X
3988X

4995X
2575
3X6 BCS

4995X
2065

5116

2554

5x11 BB

3x6 CS

5351

Correct orientation on shaft

4995X

4995X
3988X
2577
3X10 BCS

4995X
3988X

4995X
2575
3X6 BCS

5352X

(5.0 NL 4147)

5352X

4995X

4995X
2576
3X8 BCS

5352X
4147

5.0 NL

5352X

Traxxas, 1100 Klein Road, Plano, TX 75074,

TRAXXAS.com

Phone: [phone], Fax: [phone], e-mail: [e-mail]