A gearbox oil leak appearing shortly after clutch replacement is mechanically plausible as a consequence of the repair work. Clutch service requires removal or displacement of the gearbox, which disturbs seals and gaskets—particularly the input shaft seal behind the clutch release bearing, driveshaft seals, and drain/fill plugs [1][2]. The eighteen-day window between service and leak onset creates a strong temporal correlation that supports causation rather than coincidence.

Your first step is to identify the exact leak source with photographic evidence and fluid type confirmation. Check your invoice to see which components were replaced or inspected during the clutch job. Return to the garage promptly with this documentation and request a written inspection report pinpointing the leak location. If the source is a component that would have been removed, disturbed, or refilled during clutch service—especially input shaft or driveshaft seals—the garage should remedy it at no cost under their workmanship warranty [1][2].

Most reputable shops will accept responsibility if the correlation is clear and the leak originates from their work area. If the garage refuses and the leak demonstrably stems from a disturbed component, obtain an independent inspection and preserve all documentation for a potential consumer claim. The burden of proof rests on establishing that the leak source was accessed during the repair. Stop driving if the leak is significant, as low gearbox oil causes rapid transmission damage. Consult local consumer protection laws regarding garage liability, as regulations vary by jurisdiction.