The internal wiring harness for GM 4L80E transmissions is located inside the transmission pan where the wires, the loom and connectors are constantly exposed to high temperatures, mechanical vibration and transmission fluid. Over time, these parts can get hard and brittle, increasing the possibility of having potential issues down the road. For optimum performance, B&M offers this high quality plug and play replacement harness for all 1994-2003 GM 4L80E transmissions. Features include all new wiring, polyethylene wire loom, new factory style connectors, temperature sensor, rubber O-ring seal and installation instructions. Note: Can also be used on 1991-1993 4L80E models, but will require either an updated external connector to plug into the internal wiring harness, or add a B&M Shift Plus 2 controller part #120001 that allows you advanced control features to custom tune shift points, torque convertor lock-up, manual mode and more.