Off-highway vehicles (OHVs) are essential in heavy-duty industries like mining, agriculture, and construction, as equipment availability and efficiency directly affect productivity. In these harsh settings, conventional maintenance plans relying on set intervals frequently result in either early component replacements or unexpected breakdowns. This document presents a Connected Aftermarket Services Platform (CASP) that utilizes real-time data analysis, predictive maintenance techniques, and unified e-commerce functionalities to evolve OHV fleet management into a proactive and smart operation. The suggested system integrates IoT-enabled telematics, cloud-based oversight, and AI-powered diagnostics to gather and assess machine health indicators such as engine load, vibration, oil pressure, and usage trends. Models for predictive maintenance utilize both historical and real-time data to produce advance notifications for component failures and maintenance requirements. Fleet managers get practical alerts and enhanced service suggestions, reducing unexpected downtime. The platform includes an e-commerce interface that enables smooth ordering of spare parts informed by predictive diagnostics and lifecycle data of components. The system includes features like auto-generated parts lists, supplier comparisons, and inventory tracking, allowing for efficient and cost-effective maintenance activities. Simulation studies demonstrate a 21% decrease in maintenance expenses, a 32% reduction in unplanned downtime, and enhanced inventory turnover rates within the simulated OHV fleets. These findings emphasize the effect of integrated services on operational effectiveness, cost reductions, and sustainability. The CASP model reimagines lifecycle support for OHVs by establishing a digital thread from field operations to aftermarket logistics, offering a scalable, data-driven approach for contemporary fleet management.