"repair" can be either a noun or a verb, and "repairing" can be either a participle or a gerund (a verbal noun). "Under" is a preposition, and prepositions must be followed by a noun, so both "repair" as a noun and "repairing" as a gerund (verbal noun) are syntactically correct.

Versatile tractors are built, designed and developed with the same level of confidence that our new warranty provides. Full warranty includes 36-months of powertrain, hydraulics and premier component coverage.

Repair Service means providing maintenance or refurbishment on a product, entity, machine or equipment on behalf of an [insured party or customer].

Repair is to fix something that is broken. Example: I repaired the bike by fixing the seat. Replace is to get something new to replace something (broken or unbroken). Example: He replaced his flip phone with a smartphone.