A wheel loader was brought in with a catastrophic fluid loss. The operator drove into a pile, the machine suddenly lost all drive power, and a massive puddle of red transmission fluid formed under the bellhousing. The dipstick was dry. The shop pulled the transmission, assuming the front pump housing had cracked.
We separated the torque converter from the engine flexplate. Inside the bellhousing, the front pump seal was completely shredded, and the aluminum snout of the torque converter had deep, machined grooves cut into it where the seal rides. We replaced the seal and the converter, but two weeks later, the exact same failure occurred.
The root cause wasn't the seal; it was "converter walk." The torque converter is a heavy, fluid-filled donut that bolts to the engine flexplate. It slides into the front of the transmission, supported by a bushing inside the front pump. If the engine and transmission alignment are off by even a few thousandths of an inch-often caused by a loose bellhousing bolt or a worn rear engine main bearing-the heavy converter wobbles eccentrically as it spins at 2,000 RPM. This "walk" acts like an orbital sander, rapidly grinding the stationary rubber seal into the spinning converter snout until it slices through. We dialed indicated the bellhousing to the engine block and found a 0.012-inch runout. We loosened the bellhousing bolts, used shim stock to dial the alignment to zero, and the new seal lasted for thousands of hours. If a converter seal fails twice, never blame the seal; dial-indicate the housing.
