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The Rise and Legacy of Dynahoe Backhoes
Dynahoe was a prominent name in the heavy equipment industry during the mid-to-late 20th century, particularly known for its robust loader-backhoes. Originally developed by Hy-Dynamic Corporation, the Dynahoe line was later acquired by Bucyrus Construction Products and eventually NW Engineering. These machines were built for durability, with many still operating decades after production ceased. The Dynahoe 160 and 190 series, powered by Detroit Diesel 3-53 engines, featured torque converters and manual transmissions that made them versatile in both construction and agricultural settings.
Sales figures for Dynahoe machines were modest compared to giants like Caterpillar or Case, but their reputation for reliability earned them a loyal following. The 190 model, for instance, was widely used in municipal fleets and rural infrastructure projects across North America. Even today, restorers and operators seek out Dynahoes for their simplicity and mechanical accessibility.
Transmission Filter Location and Function
One of the most common maintenance challenges with older Dynahoe models is locating and servicing the transmission filter. Unlike modern equipment with clearly labeled service points, Dynahoes often require a bit of detective work. The transmission filter is typically mounted externally near the torque converter housing or along the hydraulic return line, depending on the model and year.
The purpose of the transmission filter is to trap contaminants—metal shavings, sludge, and degraded fluid particles—that can damage internal components. In machines with torque converters, the filter also helps maintain fluid cleanliness for clutch packs and planetary gears. A clogged or degraded filter can lead to slipping, delayed engagement, or complete transmission failure.
Fluid Types and Capacity Recommendations
Fluid selection is critical for Dynahoe transmissions. For the 160 series with a Borg-Warner 3-speed transmission, operators have reported using Mobilfluid 424 or equivalent tractor hydraulic fluids. This type of fluid offers anti-wear protection, thermal stability, and compatibility with wet clutch systems.
For later models like the Dynahoe 1900 equipped with a Clark 11.2 FHR transmission, Dexron III automatic transmission fluid is commonly recommended. The fluid capacity varies:
Dipstick Issues and Fluid Level Checks
A recurring issue with older Dynahoes is broken or missing dipsticks. The dipstick is usually located in a fill tube near the left brake pedal. If the stick is broken off inside the tube, fluid level checks become guesswork. In such cases, operators have resorted to measuring drained fluid volume and refilling accordingly.
A practical workaround involves:
Hydraulic Filter and Hose Maintenance
In addition to transmission filters, Dynahoe machines rely on hydraulic filters to protect steering, lift, and bucket functions. These filters are often mounted near the hydraulic reservoir or along the return line. Replacing old soft hoses is equally important, as aged rubber can crack, swell, or collapse under pressure.
One operator reported a hydraulic hose failure during testing, which led to a complete system flush and filter replacement. This highlights the importance of proactive maintenance—especially in machines with unknown service histories.
Recommended steps include:
Dynahoe’s torque converter-equipped models exhibit unique startup behavior. In some cases, the machine will move briefly upon startup but lose transmission engagement after 10 seconds. This can be caused by:
Stories from the Field
One restorer in rural Pennsylvania shared a story of reviving a 1964 Dynahoe 160 that had sat idle for 15 years. After draining a pinkish milky fluid from the transmission—likely contaminated with water—he replaced the filter, flushed the system, and filled it with Mobilfluid 424. The machine returned to service clearing brush and grading driveways.
Another operator in Alberta fabricated a new dipstick using a stainless rod and a calibrated fill chart. His Dynahoe 1900 now runs daily on a small farm, proving that with care and ingenuity, these machines can outlive their original design life.
Recommendations for Dynahoe Owners
To maintain transmission and hydraulic health in Dynahoe machines, consider the following:
Dynahoe machines may be relics of a bygone era, but their mechanical simplicity and rugged design continue to attract enthusiasts and operators. Understanding the role of transmission filters, fluid types, and maintenance protocols is essential to keeping these backhoes running smoothly. Whether restoring a barn find or maintaining a daily workhorse, attention to detail and a bit of resourcefulness go a long way in preserving the legacy of Dynahoe.
Dynahoe was a prominent name in the heavy equipment industry during the mid-to-late 20th century, particularly known for its robust loader-backhoes. Originally developed by Hy-Dynamic Corporation, the Dynahoe line was later acquired by Bucyrus Construction Products and eventually NW Engineering. These machines were built for durability, with many still operating decades after production ceased. The Dynahoe 160 and 190 series, powered by Detroit Diesel 3-53 engines, featured torque converters and manual transmissions that made them versatile in both construction and agricultural settings.
Sales figures for Dynahoe machines were modest compared to giants like Caterpillar or Case, but their reputation for reliability earned them a loyal following. The 190 model, for instance, was widely used in municipal fleets and rural infrastructure projects across North America. Even today, restorers and operators seek out Dynahoes for their simplicity and mechanical accessibility.
Transmission Filter Location and Function
One of the most common maintenance challenges with older Dynahoe models is locating and servicing the transmission filter. Unlike modern equipment with clearly labeled service points, Dynahoes often require a bit of detective work. The transmission filter is typically mounted externally near the torque converter housing or along the hydraulic return line, depending on the model and year.
The purpose of the transmission filter is to trap contaminants—metal shavings, sludge, and degraded fluid particles—that can damage internal components. In machines with torque converters, the filter also helps maintain fluid cleanliness for clutch packs and planetary gears. A clogged or degraded filter can lead to slipping, delayed engagement, or complete transmission failure.
Fluid Types and Capacity Recommendations
Fluid selection is critical for Dynahoe transmissions. For the 160 series with a Borg-Warner 3-speed transmission, operators have reported using Mobilfluid 424 or equivalent tractor hydraulic fluids. This type of fluid offers anti-wear protection, thermal stability, and compatibility with wet clutch systems.
For later models like the Dynahoe 1900 equipped with a Clark 11.2 FHR transmission, Dexron III automatic transmission fluid is commonly recommended. The fluid capacity varies:
- Dynahoe 160: Approximately 16 quarts of hydraulic transmission fluid
- Dynahoe 1900: Up to 22 quarts of Dexron III ATF
Dipstick Issues and Fluid Level Checks
A recurring issue with older Dynahoes is broken or missing dipsticks. The dipstick is usually located in a fill tube near the left brake pedal. If the stick is broken off inside the tube, fluid level checks become guesswork. In such cases, operators have resorted to measuring drained fluid volume and refilling accordingly.
A practical workaround involves:
- Draining the transmission completely and measuring the volume
- Refilling with the recommended quantity based on service charts
- Monitoring performance during operation for signs of overfill (foaming) or underfill (slipping)
Hydraulic Filter and Hose Maintenance
In addition to transmission filters, Dynahoe machines rely on hydraulic filters to protect steering, lift, and bucket functions. These filters are often mounted near the hydraulic reservoir or along the return line. Replacing old soft hoses is equally important, as aged rubber can crack, swell, or collapse under pressure.
One operator reported a hydraulic hose failure during testing, which led to a complete system flush and filter replacement. This highlights the importance of proactive maintenance—especially in machines with unknown service histories.
Recommended steps include:
- Replacing all soft hoses older than 10 years
- Installing new hydraulic filters rated for 10-micron filtration
- Using foam projectiles to clean internal hose surfaces
- Testing system pressure and flow after reassembly
Dynahoe’s torque converter-equipped models exhibit unique startup behavior. In some cases, the machine will move briefly upon startup but lose transmission engagement after 10 seconds. This can be caused by:
- Thick or contaminated fluid
- Plugged transmission filter
- Internal clutch pack wear
- Faulty pressure relief valves
Stories from the Field
One restorer in rural Pennsylvania shared a story of reviving a 1964 Dynahoe 160 that had sat idle for 15 years. After draining a pinkish milky fluid from the transmission—likely contaminated with water—he replaced the filter, flushed the system, and filled it with Mobilfluid 424. The machine returned to service clearing brush and grading driveways.
Another operator in Alberta fabricated a new dipstick using a stainless rod and a calibrated fill chart. His Dynahoe 1900 now runs daily on a small farm, proving that with care and ingenuity, these machines can outlive their original design life.
Recommendations for Dynahoe Owners
To maintain transmission and hydraulic health in Dynahoe machines, consider the following:
- Use manufacturer-recommended fluids or verified equivalents
- Replace transmission and hydraulic filters every 500 hours or annually
- Inspect hoses for softness, cracking, or bulging
- Flush systems thoroughly after contamination or long storage
- Fabricate or source replacement dipsticks if originals are missing
- Monitor for signs of slipping, delayed engagement, or overheating
Dynahoe machines may be relics of a bygone era, but their mechanical simplicity and rugged design continue to attract enthusiasts and operators. Understanding the role of transmission filters, fluid types, and maintenance protocols is essential to keeping these backhoes running smoothly. Whether restoring a barn find or maintaining a daily workhorse, attention to detail and a bit of resourcefulness go a long way in preserving the legacy of Dynahoe.
