Getting back into the hobby a little; this time with the kids. Been a long time since my RS4 MT was the best thing around.

This Arrma sale looks really good - my brother has a 223s BLX Granite and its awesome; but im wanting 3 trucks for my 7yo's - so budget wise the sale truck makes sense

Cost wise, 140 RTR is pretty good value these days i think; the truck is pretty tough. Arrma is advertising the 665 mega as "brushless ready". Lots of posts, threads, forums all say "you need a better transmission and drive line" before brushless, and arrma seems to be addressing this in the spec sheet no?

i did some additional digging based on the PDF files of exploded views between the 223s and 665
Front and rear diffs are the same by part numbers on the 223 and 665

the metal diff, mounting plate, pinons, center diff housing are different. so you could just get these parts from jenny's and drop your own dedicated hobbywing set up or whatever your desire is; if you want to get away from the spektrum 2 in 1.

(by "I" i mean gemini..)

Unique Parts: Brushless (ARA4302V4)

These parts are specific to the high-performance model and are generally designed for higher durability or compatibility with the Spektrum Firma system:

• Power System: SPMX-1081 (Motor) and SPMXSE8010RX (ESC).
• Heavy Duty Drivetrain: Parts like ARA311165 through ARA311169 (Diff gears/Input shafts) are unique to the brushless version to manage 3S LiPo power.
• Specialized Hardware: AR330535, ARA320609, and ARA320613 are utilized for the brushless motor mounting and chassis bracing.

Unique Parts: Brushed (ARA4202V4)

The "Mega" brushed model uses more cost-effective electronics and simplified drivetrain components:

• Power System: AR390143 (12T Motor) and the SPMXSE2140RXV2 2-in-1 unit.
• Gearing: Unique pinion and spur gear related items like ARA311077 and AR310779.
• Model-Specific Linkages: Small variations in items like ARA340181 and ARA311236.

Shared Parts (Common to Both)

Approximately 102 parts are shared between the two models, meaning the majority of repairs (suspension and chassis) use the same part numbers:

• Chassis: The main tub (ARA320512) and side guards are identical.
• Suspension: Arms (AR330442), shock towers, and hub carriers are universal across both platforms.
• Steering: The bellcrank and standard linkages are shared.
• Hardware: Most M3 screws, bearings (like AR610014), and body clips are the same.

Upgrade paths

To upgrade your brushed model (ARA4202V4) to the brushless (ARA4302V4) specification, you will need to swap out the electronics and reinforce the drivetrain to handle the increased power.

1. Essential Electronics (The Power Swap)

The most direct change involves replacing the 2-in-1 ESC/Receiver unit and the motor.

• Brushless Motor: SPMX-1081 (Firma 3660 3200Kv Brushless Motor).
• ESC/Receiver Unit: SPMXSE8010RX (Firma 85A Smart 2-in-1 ESC and Receiver).
• Motor Mounting: You will need the brushless-specific motor mount plate, ARA311192, to properly secure the new motor.

2. Drivetrain Reinforcement (Durability)

The brushless model uses metal internal components that are unique to that platform to prevent "stripping" gears under 3S LiPo power.

• Metal Diff Internals: Replace the standard gears with the heavy-duty set including ARA311165, ARA311166, and ARA311167.
• Input Shafts: Use the brushless-spec input shafts, ARA311169, which are designed for higher torque.
• Slipper Clutch/Spur Components: Components like ARA310998 and ARA311192 are specific to the brushless power delivery system.

3. Necessary Hardware & Bracing

There are a few smaller unique items used in the brushless assembly to manage heat and vibration:

• Motor Heat Sink/Fan Hardware: Ensure you have the mounting screws and brackets such as AR721308 and AR723310.
• Chassis Bracing: The brushless version utilizes specific spacers and mounts like ARA320609 to stiffen the assembly.

Upgrading the 665 to 223s drivetrain from jennys rc

To upgrade your brushed model (ARA4202V4) to the brushless (ARA4302V4) specification for drivetrain reinforcement using JennysRC.com, it is most cost-effective to buy factory-assembled units. Buying these "take-off" parts is significantly cheaper than buying individual gears and bearings separately.

Based on current market pricing for the Big Rock 3S / Granite 3S platform, here is the estimated total cost:

Required Reinforcement Assemblies

To handle the power of a brushless system, you must replace the plastic/composite internal components with the heavy-duty metal versions found in the BLX models.

Component	Function	Estimated Price
Front Differential Assembly	Replaces plastic internals with metal gears	$21.97
Rear Differential Assembly	Replaces plastic internals with metal gears	$21.97
HD Slipper Clutch Assembly	57T 0.8Mod metal spur gear and heavy-duty pads	$22.97
Aluminum Motor Mount Set	Required for brushless motors; includes heatsink and fan	$21.97
Center Slider Driveshaft	Reinforced shaft for the longer 3S wheelbase	$9.34
Estimated Subtotal		$98.22

Total Estimated Cost

• Parts Subtotal: ~$98.22
• Shipping: Approximately $6.00 – $8.00 for standard US shipping.
• Total Project Cost: ~$105.00

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Why these specific parts?

1. Differentials: The brushed model uses composite gears that will likely strip immediately under 3S brushless torque. The BLX assemblies from JennysRC come pre-filled with oil and are ready to drop in.
2. Slipper Clutch: The brushed "Mega" slipper uses a different gear pitch (48P) and weaker pads. The 0.8Mod/32P HD slipper is the standard for brushless durability.
3. Motor Mount: The brushed model uses a fixed plastic mount. You must have the aluminum sliding mount to adjust gear mesh for different brushless pinions.