Chevrolet Silverado 2500 Rear Main Seal Replacement Cost

The rear main seal is the mechanical seal on the end of the crankshaft, often seated in a housing that attaches to the rear of the engine block.

The engine's crankshaft protrudes slightly from the rear of the engine block so that it can connect to the transmission. The rear main seal covers the perimeter of the crankshaft end to keep the circulating oil inside the engine.

An oil leak may be noted on the ground where the vehicle is parked. The leak will appear to be coming between the engine and the transmission, but over time can coat the underside of the car near the engine. In extreme cases, the leaking oil will be being to coat the flywheel, and can cause clutch slippage in vehicles equipped with a manual transmission.

A vehicle can still be driven with a leaking rear main seal. However, it will become necessary to check the oil and top the oil level off more often. A leaking rear main seal increases the risk of driving with insufficient oil in the engine, starving oil driven parts. Damage to timing chain tensioners, camshaft bearings, crankshaft bearings, and other oil lubricated components is probable if the vehicle is driven with low oil.

Repair intervals vary greatly by vehicle and driving conditions. The rear main seal does not wear like a tire or a ball joint, but eventually the gasket's rubber will degrade to the point of leakage. Due to the rear main seal location, it is often not noticed unless the transmission is off for servicing.

It is easiest to spot oil leaks when they are new or fresh. The technician may clean the fluid around the leak and direct you to come back later to confirm where the leak is coming from. With more progressed oil leaks, the technician will also add a dye to the oil. After the vehicle has been driven with the dye, a UV light will be used to pinpoint the leakage and recommend repair.

The technician will remove the transmission and flywheel or flexplate from the vehicle to access the rear main seal. Depending on the vehicle, the seal is either removed from the engine block, or the housing that holds the rear main seal is removed in its entirety. The mating surfaces for both sides are cleaned, and the new rear main seal is installed. The transmission will be installed, and the technician will check for leaks to ensure a proper repair.

Proper diagnosis is needed to pinpoint the leak. An external head gasket leak, a split line, or a more expensive transmission leak could be the source of the fluid. If equipped, the clutch in a manual transmission vehicle should be serviced, as it has to be removed in order to access the rear main seal. Transmission mounts and driveshaft support bearings should be inspected for wear and replaced if necessary.

Oil is damaging to rubber components like hoses, belts, and motor mounts. Continued oil leaks onto the these components will cause premature failure. With a rear main seal leak, it also becomes even more important to check the oil level. The oil in the lubrication system is under pressure, so driving with an oil leak is forcing oil out of the seal. An oil leak increases the risk of driving with insufficient oil in the engine, starving oil driven parts. Damage to timing chain tensioners, camshaft bearings, crankshaft bearings, and pistons is probable if the vehicle is driven with low oil.

Repairing your own car is an extremely rewarding process that can also save you money. But before you dive in, it’s important to be sure the issue has been properly diagnosed. Seemingly obvious symptoms can lead the inexperienced down a rabbit hole of replacing parts that don’t fix the problem. Proper diagnosis can save more money than guessing at what’s broken! If you're unsure you have the right tools or experience to diagnose a problem, consider reaching out to a RepairPal Certified Shop. Replacing the rear main seal requires removal of the transmission and the flywheel or flexplate. Depending on the design of the seal, it may also require removal of the oil pan, and removal of the crankshaft in order to replace rear main seal housings (where applicable). Due to the advanced nature of this job, it is extremely important to research the procedures before ordering parts or attempting this repair. We recommend having a professional replace this part.