CMAX Assembly Instructions

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GCM CMAX ASSEMBLY INSTRUCTIONS

These assembly instructions will help you put together your CMAX chassis. It’s best to think of this as a guide that provides a baseline for your build rather than instructions that must be followed to the letter. The inherent flexibility designed into the CMAX platform allows you easily to adjust almost all aspects of your setup to suit your particular build.

Contents
1. Low-range Transmission
2. LRT2 Transfer Case
3. Chassis
4. TM8 Axles
5. Suspension
6. Electronics
7. Body Mounts

Each section includes reference pictures and links to GCM build videos to help you through your build. Enjoy!!!
 

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1. Low-Range Transmission

We recommend starting with the transmission and transfer case. The GCM Low-Range Transmission ships mostly pre-assembled and looks like this out of the package:

DSC07343.jpg

To complete the transmission, you will need to install the motor plate, motor, input gear/shaft, and output shaft.

Step 1.1: Grease transmission

Before beginning the assembly, we recommend adding grease to the joints in the transmission housing to provide additional protection from water and mud. This is easiest to do one section at a time beginning with the section closest to the motor, adding marine grease to the flanges between adjoining sections:
DSC07703.jpg

DSC07705.jpg

Although the transmission gears come pre-greased, this is a good time to check and add grease as needed/preferred.

When you get to the rear-most section of the transmission, leave the last section of the housing unassembled after greasing and proceed to Step 1.2.

Step 1.2: Add output shaft

Remove the output shaft, bearings and gears from the package:
DSC07713.jpg

Install bearings into output end of transmission housing:
DSC07714.jpg

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DSC07716.jpg

Add output gear and pin to output shaft and install shaft:
DSC07723.jpg

DSC07727.jpg

Re-install end of transmission housing:
DSC07728.jpg

Use hex driver inserted through output shaft in hole to make sure everything spins smoothly.

Step 1.3: Add motor plate, motor and input shaft

Remove the motor plate, input shaft/gear, bearing and pinion from package:
DSC07755 cropped.jpg

Add bearing to motor plate:
DSC07769.jpg

Place input shaft in motor plate:
DSC07770.jpg

Add motor and pinion to motor plate leaving motor screws snug but not tight:

DSC07773.jpg

To set proper pinion mesh, adjust the motor height so that there is approximately 2-3mm of vertical play in the input shaft/gear. Here?s a video showing how much vertical play you should have in the input shaft/gear:

Install motor plate with 3 screws (top center and one on each side) to test mesh:
DSC07775.jpg

Continued in next post...
 

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After installing the motor plate and motor, you should be able to spin the entire motor/transmission combination using a hex driver in the output shaft with no binding or grinding of gears. Here’s another video showing this step:

Adjust pinion mesh if needed and re-test. Once mesh has been set properly, add the remaining motor plate screws using thread lock.

2. LRT2 Transfer Case

The LRT2 transfer case can be installed in either left-drop or right-drop configuration. If your build is left-drop, install half of t-case housing like this:
DSC07733.jpg

If your build is right-drop, install half of t-case housing like this:
DSC07731.jpg

Install bearings into both halves of transfer case housing:
DSC07736.jpg


Install pin and gear on transfer case output shaft. Pin and gear are installed on the side with the smaller hole:
DSC07748.jpg

Add t-case input gear and pin to transmission output shaft, followed by middle gear and t-case output gear/shaft:
DSC07750.jpg

Install second half of t-case housing using single pass-through screw. Note that pass-through screw will be inserted from rear to front in right-drop configuration and from front to rear in left-drop configuration:
DSC07470.jpg DSC07752.jpg

Install transfer-case mounting bracket onto back of transfer case:
DSC07757.jpg

Install grub screws in the 2 holes above the transfer-case mounting bracket:
DSC07758.jpg

Note that these 2 holes above the mounting bracket are completely pass-through, so you will to stop screwing the grub screws when the ends of the screws are flush with the outer surface of the housing.

Your completed transmission/transfer case assembly should look like this (right-drop):
DSC07778.jpg
 

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3. Chassis

Step 3.1: Install transfer case/transmission/motor assembly

The transfer case/transmission/motor assembly mounts to the CMAX chassis by screwing the transfer case mounting bracket into underside of chassis rails and inserting the motor plate tabs into the c-channels in the chassis rails:
IMAG1986.jpg

IMAG1987.jpg

The CMAX frame rails include 10 pre-tapped mounting positions for the transfer case mounting bracket, allowing you to adjust the placement of the entire Low-Range Transmission/LRT2 transfer case assembly with just 2 screws:
DSC07787.jpg

Because the CMAX chassis was designed with multiple mounting options for virtually all of the major components, you can choose mounting locations that best suit your particular build. GCM has prepared setup sheets showing recommended mounting locations and configurations for many of the popular, widely available 1/10th scale hard bodies on the market. We will be updating these instructions as well as the CMAX guide on Scale Builder’s Guild with setup sheets. We encourage you to experiment with setups to find the one that works best for your particular build.

Step 3.2: Install servo mount

IMAG1988.jpg

Note that the servo mount is designed for the cross plate to sit in front of the servo and drop between the rails:

Step 3.3: Install rear cross-brace

The CMAX rear cross-brace provides structural support for the chassis and a damper mounting location for leaf-sprung setups. It also has pre-tapped holes that can be used for mounting bodies or accessories.
IMAG1998.jpg

If you are not sure what location will work best for your build, you can leave the cross brace loose within the frame rails until you have installed the suspension, body mounts and receiver box.

Step 3.4 (optional): Install additional cross brace

CMAX kits include an extra cross brace that you can use for mounting bumpers or other accessories. Here is a picture showing the additional brace installed at the front of the chassis for later front bumper mounting:
IMAG1989.jpg
 

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4. TM8 Axles

TM8 axles are available in a variety of configurations to suit your build. There are 4 different front axle housing versions (left drop leafed, left drop linked, right drop leafed, and right drop linked) to go along with 2 rear axle housing versions (leafed or linked, both with centered pumpkins). All of the versions use the same hardware (bearings, CVDs, rear axle shafts, knuckles, rear bearing caps, etc) and damper mounting locations.

DSC07831.jpg

Because TM8 axles are based on the Vaterra Ascender architecture, assembling them is very similar to assembling an Ascender axle. Here is a link to a GCM video with general tips on TM8 assembly:


Before beginning assembly of the TM8 axles, we recommend using a 3/32? drill bit in all of the screw mounting holes to clean out any excess material from the printing process.

Step 4.1: Install front axle locker and pinion

Start by installing bearings for GCM Universal Diff Input:
IMAG2013.jpg

IMAG2014.jpg

You can use a 1/2" socket to press on the inner bearing so that it seats all the way in:
IMAG2016.jpg


Install GCM Universal Diff Input:
IMAG2017.jpg


Install pinion gear inside axle housing:
IMAG2019.jpg


Add bearings to locker and install locker and make sure to add plenty of grease to the ring and pinion gears:
IMAG2020.jpg

Install diff cover:
IMAG2022.jpg

Step 4.2: Install front axle CVDs and knuckles
Add bearings to each CVD:
IMAG2027.jpg

Install CVDs into axle housing:
IMAG2028.jpg

Add bearings, flanges, and set screws to knuckles as shown:
IMAG2029.jpg

IMAG2030.jpg

IMAG2031.jpg

Add washers (3 per side), hex pins and hexes:
IMAG2032.jpg

Step 4.3: Install steering links


Rear axle instructions continue in next post...
 

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Step 4.3: Install rear axle locker and pinion

Repeat step 4.1 with rear axle housing and hardware:
DSC07834.jpg

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Step 4.4: Install straight rear axle shafts

Insert shafts into axle:
DSC07845.jpg

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Install diff cover:
DSC07852 cropped.jpg

Add bearings onto the the ends of the axle shafts:
IMAG2023.jpg

Install bearing caps:
IMAG2024.jpg

Add spacer to end of axle shaft, followed by hex pin and wheel hex:
IMAG2025.jpg

IMAG2026.jpg
 

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5. GENERAL SUSPENSION NOTES

We recommend installing the front suspension before the rear suspension. Most bodies will work best with the baseline front suspension configurations (one leafed and one linked) shown in section 5 below. Once you have installed the front suspension, you can then set the rear suspension configuration (leaf mounting locations or combination link length/coil bucket mounting location) for your build. If you are using one of the popular hard bodies, we recommend using the GCM setup sheets for that body. If there is no setup sheet for the body you are using, you can easily adjust the suspension, transmission/transfer case, and body mount locations to suit your particular build.

CMAX is designed to use 58-60mm dampers (uncompressed length) front and rear in both leaf-sprung and linked suspension configurations. If you are supplying your own dampers for your build, GCM recommends the ECX 1/18th shocks (part number ECX213000), which are 58mm from eye to eye. The RC4WD Ultimate Scale 60mm shocks are another widely available option that work very well with CMAX.

If you are using a linked suspension in the front and/or rear, you will need to supply 12.5x60mm springs (standard size for the Axial SCX-10). Axial makes these springs in 5 different stiffnesses ranging from 1.13 lbs/in to 3.03 lbs/in. We recommend using the stiffest spring (part number AX31442, Blue 3.03 lbs/in) for most builds.
 

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6. Front Suspension

Step 6.1: Prepare Dampers
If you are using the ECX shocks, prepare them as follows. First, remove coil springs, spring pre-load collar, and spring retainer cup:
DSC07900 cropped.jpg

DSC07902.jpg

Remove ball from lower ball ends of each damper:

DSC07904.jpg

DSC07906.jpg

ECX 1/18th shocks come pre-filled with oil and do not need to be refilled unless you prefer a different oil weight.

If you are using the RC4WD 60mm Ultimate Scale Shocks or other shocks, remove any internal or external springs and fill with oil before installation.

Step 6.2: Link plate installation

If you plan to use links in either the front or rear, install the side link plates using the upper two screw mounting positions:
DSC07945.jpg

Note the 3mm spacers to be installed between the link plate and the chassis rails:
Side plate 1.jpg

Note that the smooth sides of the link plates face away from the rails:
Side plate 2.jpg

Here is a short installation video for the link plate:

Step 6.3: Leaf-sprung front suspension installation
Install front leaf hangers in baseline position leaving 2 empty holes in the chassis ahead of the hangers:

IMAG2010.jpg


Install front swing shackles in the fourth hole from the end of the front leaf mount holes using the included washers between the shackles and frame rails:
IMAG1993.jpg

Screws for the leaf hangers and front swing shackles are inserted from inside the frame rails.

If you are using leaf springs in front and rear, note that the front swing shackles are shorter than the rear shackles.

Here is GCM's leaf suspension installation video:

Skip to Step 6.5: Front damper installation
 

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Step 6.4: Linked front suspension installation

Install upper shock mount/coil bucket in baseline location (front-most mounting position on raised section of chassis rail):
IMAG2005.jpg

Assemble links:

CMAX links.jpg

Link assembly video:

Attach links to side plate using included 3mm spacers for clearance:

IMAG2007.jpg

Attach links to axles (TM8 axles shown):

IMAG2008.jpg

Note placement of 5mm spacer between side plate and front upper link:

IMAG2006.jpg

Step 6.5: Install front dampers

If using ECX shocks, use flat head screws, o-rings, and lock nuts included in the GCM combo kit by placing one o-ring on either side of each shock mount (upper and lower) and an M3 lock nut on the upper shock mount screw before attaching shock mount screws to the chassis and axles:

IMAG1990.jpg

Installed with leaf suspension:
IMAG2010.jpg

Installed with linked suspension:
IMAG1991.jpg

IMAG1992.jpg

Installation video for dampers on leaf-sprung suspension:

If front suspension is linked, install coils in coil buckets:
IMAG2005.jpg

Installation video for dampers and coils on linked suspension:
 

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7. Rear Suspension

If you are using a body for which GCM has prepared a setup sheet, refer to the setup sheet for recommended rear suspension mounting locations and link lengths (if applicable) for your build. If you are using a body for which there is no GCM setup sheet, adjusting the the wheelbase at the rear axle to suit your build is very simple, as you will see below.

Step 7.1: Leaf-sprung rear suspension installation

Install rear leaf hangers:
IMAG1995.jpg

Intall rear swing shackles using included flange on the chassis side of each shackle:

DSC07816.jpg

DSC07820.jpg

IMAG1996.jpg

IMAG1997.jpg

Attach leafs to axles and chassis:
DSC07913.jpg

Install shocks. If using ECX 1/18 shocks, refer to step 6.5 for mounting instructions. Note there are 2 options for mounting the dampers at the chassis.

Option 1: Mount dampers to chassis using the rear cross-brace:
IMAG1998.jpg

Option 2: Mount shocks outside the rails using the GCM Tiny Shock Mounts (sold separately):
CMAX rear leaf shock mount.jpg

Lower damper mount:
IMAG1999.jpg

Installation video for rear leaf spring suspension:

Installation video for dampers on leaf-spring setups:
 

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Step 7.2: Linked rear suspension installation

GCM offers rear link kits to fit a range of wheelbase options:
- 277mm (10.9") fits from 274-280mm (10.8"-11")
- 308mm (12.1") fits from 305-311mm (12"-12.2")
- 330mm (13") fits from 327-333mm (12.8-13.1")

If you are using the GCM front links, you can also adjust the wheelbase at the front by an additional + or - 3mm. If you are using a body with a different wheelbase, you can make your own links to suit your build.

Start by assembling your links:
CMAX links.jpg

Link assembly video:

Attach links to side plates:
IMAG2003.jpg

Note the use of 3mm spacers inside the c-channel rails for proper spacing of the upper links:
IMAG2000.jpg

Attach links to axle:
[picture to be added]

Install dampers and coils. If using ECX 1/18 shocks, refer to step 6.5 for mounting instructions:
IMAG1991.jpg

Damper installation video:
 

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In case you missed it, Roo ran into a little snag assembling a t-case this afternoon while Dad was working in the yard.

Roo at the bench 1.jpg

So he took it upon himself to post his sentiments thusly:

HELP HELP THIS THING IS IMPOSSIBLE TO BUILD!!!!!!!!!!!!!!!!!
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:blackeye: But we got through it. Did I mention he's now built more of these things than Dad has...? :shhh:
 
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