Team C TM4 Buggy Build – Part 3 – Gearboxes

The Build – Part 3
Diffs are built so it’s time to install them in the gearboxes and get the gearboxes attached to the chassis.

Build Notes:
This build step is pretty easy, just pay attention to which gearbox and center drive axle you use. The gearboxes have different output angles while the drive axles are different lengths. I’ll explain it better in each step.

A shart eye will notice that the differential build ended with Step 14 and that this part of the build is starting with Step 14. Oops on my part. Too much work to relabel all the pix so we’re starting off with Step 14. Deal with it.

Let’s first get aquainted with the two different gearboxes. The one on the left is the front box; notice the angled output opening. This angle takes into consideration the kickup built into the front of the TM4; the axle is straight once it is installed. The gearbox on the right is the rear box. We’ll be building the front gearbox first.

Now assemble your center drive axles. You’ll see the shafts come in two lengths: an 95mm shaft (the rear shaft; the one on top) and an 85mm shaft (the front shaft; the one on the bottom). Grab the 85mm shaft since we’re working on the front of the TM4. If you get confused, the lengths are printed right on them.

We also have to take a quick look at the gearbox covers; the front and rear ones differ as well. The red arrow points to the different clearance area the front cover has that the rear one does not need. Grab the front cover (the one on the left) and keep it handy for the front gearbox build.

Attach the FR arm mount to the front gearbox as shown. ‘FR’ stands for ‘F’ront of the car, ‘R’ear mount (or inner mount).

Slide two 5×8 washers onto the front drive axle followed by a 5×10 bearing. Once seated, slide the assembly into the gearbox opening.

Holding the axle in place, slide another 5×10 bearing onto the shaft followed by a 16t sungear. The gear should slide all the way onto the axle; secure with the M3x8 screw. A dab of threadlocker here is suggested.

Slide your front diff assembly into the gearbox as shown, pressing it in to make sure the bearings set into place. The diff NEEDS to be assembled in this direction. Now slide the front gearbox cover into place and screw together.

Fit the front gearbox to the chassis and secure. The orange FR arm mount might make positioning it a little difficult so just take your time.

Here is what your front gearbox should look like installed.

We’ll do basically the same thing with the rear gearbox install. Attach the RF arm mount to the rear gearbox. ‘RF’ stands for ‘R’ear of the car, ‘F’ront mount (or inner mount). Yes, it seems oddly backward from the front but once it’s assembled you’ll understand it.

Using your 95mm center axle, slide two 5×8 washers and a 5×10 bearing onto it. Press this assembly into the rear gearbox.

Holding the axle in place, slide another 5×10 bearing onto the shaft followed by a 16t sungear. The gear should slide all the way onto the axle; secure with the M3x8 screw. A dab of threadlocker here is suggested.

Slide your rear diff assembly into the gearbox as shown, pressing it in to make sure the bearings set into place. The diff NEEDS to be assembled in this direction. Now slide the rear gearbox cover into place and screw together.

Set the gearbox assembly onto the chassis and secure.

You can grab the center axles and rotate them to make sure everything feels free. Another step down, another step closer.

Team C TM4 Buggy Build – Part 1 – Main Chassis Prep
Team C TM4 Buggy Build – Part 2 – Differentials
Team C TM4 Buggy Build – Part 3 – Gearboxes
Team C TM4 Buggy Build – Part 4 – Center Clutch
Team C TM4 Buggy Build – Part 5 – Steering
Team C TM4 Buggy Build – Part 6 – Top Deck/Shock Towers
Team C TM4 Buggy Build – Part 7 – Front Suspension
Team C TM4 Buggy Build – Part 8 – Rear Suspension
Team C TM4 Buggy Build – Part 9 – Shocks
Team C TM4 Buggy Build – Part 10 – Electronics
Team C TM4 Buggy Build – Part 11 – Wheels, Tires, Body

Back to the Team C TM4 Buggy Build List