VehiclesArrma Quake Grom MEGA 380

Arrma Quake Grom MEGA 380

1/16 scale · monster truck · ARA2137

Final drive: 11.73:1

Open in Top Speedsourced

Arrma Quake Grom MEGA 380 — Photo: Horizon Hobby

Specifications

Last modified Sep 23, 2026

Spec	Value	Basis
Drivetrain
Pinion	13TStock	Stock
Spur	61TStock	Stock
Transmission & axle	2.50:1Derived	Derived
Final drive	11.73:1Stock	Stock
Wheels & tires
Tire diameter	Not published
Power
Motor	Not applicable
Motor shaft	Not published
Battery	Up to 2SLiPoStock	Stock
Performance
Theoretical top speed	Not applicable
Vehicle
Part number	ARA2137
Scale	1/16
Class	Monster truck

Stock is as the vehicle ships. Calculated is worked from the stock figures on this page rather than stored beside them, so the two cannot drift apart. Derived is worked out from gear tooth counts the maker publishes rather than printed as a ratio; the notes below say how. Not applicable means the vehicle does not come with it, like the motor on a roller or the tires on a race kit, or does not have one, like a KV rating on a brushed motor. Not published means it exists but no source we could find prints it.

Gearing parts

Pinion and spur parts for the Arrma Quake Grom MEGA 380: fitted, and optional gearing supplied in the box
Component	Teeth	Pitch	Bore	Part number
Fitted at the factory
Pinion	13T	Mod 0.5	2.3 mm	ARA-2628 (opens in a new tab)
Spur	61T	Mod 0.5	Not applicable	ARA-2592 (opens in a new tab)

Tooth counts are the ones in the specifications above. Pitch is given as metric module (Mod 1, Mod 0.8) or diametral pitch (32P, 48P). They are different standards and are not interchangeable, even where the numbers look close. Bore is the pinion’s hole, listed separately from the motor shaft. Linked part numbers go to the maker's or official distributor's page for that part.

How these numbers were settled

A 1/16 brushed Grom monster truck, sold with a battery and charger, with an Arrma MEGA 380 brushed motor and a Spektrum 25A 2-in-1 ESC and receiver; Horizon lists 2S LiPo compatibility.

Brushed, so there is no KV.
Horizon prints Pinion 13T and Spur Gear 61T.
The transmission and axle ratio is not printed for the brushed Groms; the standard-parts list names the same 30T Grom diff (or its oil-filled 30T twin) and the same input gear set (ARA311182, two 12T input gears) that Horizon prints as a 2.50 ratio on the brushless Grom 223S trucks, so 30/12 = 2.5 is used.
Final drive is 61/13 x 2.5 = 11.73.
No diameter is published for the dBoots Chevron MT Grom tire, so it is left blank.

Documents

ManualInstruction manual (Horizon PDF) (opens in a new tab)
Exploded viewExploded view (Horizon PDF) (opens in a new tab)13T STD pinion, motor and 61T spur
Parts listTech pack with pinion options, STD/OPT marked (Horizon PDF) (opens in a new tab)Pinion options, p. 2

Sources

Every figure on this page traces to one of these. Where they disagreed, the note above says which was used and why.