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The Case 350 Crawler and Its Industrial Footprint
The Case 350 crawler loader was introduced in the late 1960s and remained in production through the 1970s, serving as a compact yet capable machine for grading, loading, and light earthmoving. Built by J.I. Case Company—founded in 1842 and later merged into CNH Industrial—the 350 series was part of Case’s push to offer affordable tracked machines for contractors, municipalities, and farmers. With an operating weight of around 12,000 lbs and powered by a 4-cylinder diesel engine, the 350 was known for its mechanical simplicity and field serviceability.
Though not produced in massive volumes compared to larger Case crawlers like the 1150, the 350 earned a loyal following, especially in Canada and the northern U.S., where its compact footprint and torque converter transmission made it ideal for tight job sites and cold-weather starts.
Transmission Oil Loss from the Bell Housing
A common issue reported in aging Case 350 units is the loss of transmission oil from the bell housing area—often measured at about one quart per eight hours of operation. This leak typically points to internal seal failure within the shuttle transmission or torque converter assembly.
The bell housing serves as the protective enclosure between the engine and transmission, housing the torque converter and input shaft. When oil escapes from this area, it suggests that pressurized fluid is bypassing a seal or that a component has cracked internally.
Charge Pump Seal and Torque Converter Spout
The most likely culprit is the seal at the charge pump, which supplies hydraulic pressure to the shuttle transmission. This seal is located near the torque converter’s spout—a critical interface where fluid is transferred from the converter to the transmission. If the spout is worn, pitted, or misaligned, the seal cannot maintain pressure, resulting in a slow but persistent leak.
In some cases, the torque converter itself may be cracked, especially if the machine has experienced hard impacts or overheating. A hairline fracture in the converter housing can allow fluid to seep into the bell housing and drip from the bottom drain hole.
Inspection and Removal Procedure
To confirm the source of the leak, the shuttle transmission must be removed. This involves:
Field Anecdotes and Operator Wisdom
One diesel fitter in Queensland recalled a similar issue on a Case 350 used for clearing fence lines. The machine leaked oil steadily from the bell housing, and after removing the shuttle, they discovered the converter spout had worn into an oval shape. The seal had no chance of holding pressure. A replacement spout and seal resolved the issue, and the machine returned to service with no further leaks.
Another operator in Ontario shared that his 350 had a leak that worsened in cold weather. The seal shrank slightly in freezing temperatures, allowing more fluid to escape. He installed a block heater to keep the transmission warm overnight, which reduced the leak until a full teardown could be scheduled.
Preventive Maintenance and Recommendations
To prevent transmission oil loss in Case 350 crawlers:
Conclusion
The Case 350 crawler remains a dependable machine decades after its release, but transmission oil loss from the bell housing is a warning sign that demands attention. Whether caused by a failed charge pump seal or a cracked torque converter spout, the solution requires careful inspection and precise repair. With proper maintenance and field-tested wisdom, these machines can continue to serve operators in grading, loading, and land clearing tasks—proving that even vintage iron has plenty of life left when treated right.
The Case 350 crawler loader was introduced in the late 1960s and remained in production through the 1970s, serving as a compact yet capable machine for grading, loading, and light earthmoving. Built by J.I. Case Company—founded in 1842 and later merged into CNH Industrial—the 350 series was part of Case’s push to offer affordable tracked machines for contractors, municipalities, and farmers. With an operating weight of around 12,000 lbs and powered by a 4-cylinder diesel engine, the 350 was known for its mechanical simplicity and field serviceability.
Though not produced in massive volumes compared to larger Case crawlers like the 1150, the 350 earned a loyal following, especially in Canada and the northern U.S., where its compact footprint and torque converter transmission made it ideal for tight job sites and cold-weather starts.
Transmission Oil Loss from the Bell Housing
A common issue reported in aging Case 350 units is the loss of transmission oil from the bell housing area—often measured at about one quart per eight hours of operation. This leak typically points to internal seal failure within the shuttle transmission or torque converter assembly.
The bell housing serves as the protective enclosure between the engine and transmission, housing the torque converter and input shaft. When oil escapes from this area, it suggests that pressurized fluid is bypassing a seal or that a component has cracked internally.
Charge Pump Seal and Torque Converter Spout
The most likely culprit is the seal at the charge pump, which supplies hydraulic pressure to the shuttle transmission. This seal is located near the torque converter’s spout—a critical interface where fluid is transferred from the converter to the transmission. If the spout is worn, pitted, or misaligned, the seal cannot maintain pressure, resulting in a slow but persistent leak.
In some cases, the torque converter itself may be cracked, especially if the machine has experienced hard impacts or overheating. A hairline fracture in the converter housing can allow fluid to seep into the bell housing and drip from the bottom drain hole.
Inspection and Removal Procedure
To confirm the source of the leak, the shuttle transmission must be removed. This involves:
- Draining transmission fluid and disconnecting hydraulic lines
- Removing the loader frame crossmembers for access
- Unbolting the bell housing and separating the engine from the transmission
- Inspecting the torque converter spout and charge pump seal
- Checking for cracks or scoring in the converter housing
Field Anecdotes and Operator Wisdom
One diesel fitter in Queensland recalled a similar issue on a Case 350 used for clearing fence lines. The machine leaked oil steadily from the bell housing, and after removing the shuttle, they discovered the converter spout had worn into an oval shape. The seal had no chance of holding pressure. A replacement spout and seal resolved the issue, and the machine returned to service with no further leaks.
Another operator in Ontario shared that his 350 had a leak that worsened in cold weather. The seal shrank slightly in freezing temperatures, allowing more fluid to escape. He installed a block heater to keep the transmission warm overnight, which reduced the leak until a full teardown could be scheduled.
Preventive Maintenance and Recommendations
To prevent transmission oil loss in Case 350 crawlers:
- Monitor fluid levels daily and inspect for drips under the bell housing
- Use high-quality transmission fluid with proper viscosity for ambient temperature
- Install a magnetic drain plug to catch metal particles from internal wear
- Schedule seal replacement every 2,000 hours or during clutch service
- Avoid overloading the machine, which increases torque converter stress
- Keep the torque converter area clean to spot leaks early
Conclusion
The Case 350 crawler remains a dependable machine decades after its release, but transmission oil loss from the bell housing is a warning sign that demands attention. Whether caused by a failed charge pump seal or a cracked torque converter spout, the solution requires careful inspection and precise repair. With proper maintenance and field-tested wisdom, these machines can continue to serve operators in grading, loading, and land clearing tasks—proving that even vintage iron has plenty of life left when treated right.
