3126 slotEnsure that the bearing tab engages with the slot in connecting rod cap (4) . 3.Place clean engine oil on the pistons, the piston rings, the cylinder bore, the upper half of the connecting rod bearing, and the lower half of3126 engine applications Caterpillar 3126 engines are used in many work applications such as delivery trucks, dump trucks, garbage trucks, snow plows, flatbed trucks and school buses.