Serving within the 212th Attack Battalion, Gearshift was a clone trooper fighting for the Grand Army of the Republic during the Clone Wars. During the Second Battle of Geonosis, he met his death at the hands of undead Geonosians controlled by the hive of Queen Karina the Great.
Within the ranks of the Grand Army of the Republic was Gearshift, a clone trooper. Early in the conflict of the Clone Wars, Jedi General Obi-Wan Kenobi found himself, along with several members of the 212th Attack Battalion including Gearshift, as a prisoner of General Grievous on the icy moon of Caliban, situated in the Outer Rim Territories. Grievous demanded that the Galactic Republic troops reconstruct a bridge, previously destroyed during the Separatist invasion of the moon, under threat of death.
Following an argument between Kenobi and Grievous, Grievous's terms were accepted. However, a scheme to deliberately sabotage the bridge was conceived, but then abandoned upon the discovery that a native of the moon, a Qubey, had been separated from its kin. Cooperation with the Qubey allowed them to formulate an escape plan.
Upon the bridge's completion, Grievous revealed his intention to abandon the prisoners on the moon. The subsequent attack by the Qubey served as a distraction for Grievous and his forces, which allowed the clones to seize E-5 blaster rifles from the B1-series battle droids. The Qubey triggered an avalanche, which buried Grievous and his forces. Kenobi and the clones then made their escape from the moon aboard their LAAT/i gunship, destroying the bridge as they left.
After the Geonosis primary droid foundry was destroyed by Republic forces, the search for Separatist leader Poggle the Lesser commenced. When Jedi Master Luminara Unduli and clone trooper Buzz did not return from their patrol, Jedi Generals Anakin Skywalker and Obi-Wan Kenobi assembled a rescue team. Gearshift, along with Clone Commander Cody, was selected to enter the Geonosian catacombs in order to locate the missing soldiers.
Upon their arrival, they discovered Buzz, deceased, along with Unduli's lightsaber, prompting them to search the catacombs in hopes of finding Unduli. Their search led them to encounter undead Geonosians. Kenobi, alarmed by this discovery, dispatched Gearshift and another trooper to the surface to contact their forces. However, Gearshift and his comrade were overwhelmed and killed before they could complete their mission.
On Caliban, Gearshift was equipped with HT-77 Cold Assault Armor featuring orange markings, which signified his affiliation with the 212th Attack Battalion. During the Geonosis mission, he wore Phase I clone trooper armor, and he was armed with a DC-15A blaster carbine.