Evaluating the Longevity and Rebuild Potential of the John Deere 670B Motor Grader

[MikePhua]

The 670B and Its Place in Deere’s Grader Lineage
The John Deere 670B motor grader was introduced in the late 1980s as part of Deere’s B-series, which marked a transition toward more refined hydraulic control, improved operator visibility, and enhanced serviceability. Built for mid-range grading tasks, the 670B was widely used in municipal road maintenance, site preparation, and light construction. Deere’s grader legacy dates back to the 1960s, but the B-series helped solidify its reputation for reliability and parts support.
Powered by a naturally aspirated or turbocharged diesel engine, the 670B offered a balance of torque and fuel efficiency. Its transmission, typically a powershift unit, allowed for smooth gear changes under load—critical for maintaining consistent grading speed. By the mid-1990s, thousands of 670Bs had been sold across North America, many of which remain in service today.
Assessing Engine Life at 12,000 Hours
A 670B with over 12,000 operating hours is approaching the upper threshold of its expected engine life. While Deere engines are known for durability, most contractors consider 10,000–12,000 hours to be the point where major components—especially the engine—may require overhaul. However, longevity depends heavily on maintenance history, operating conditions, and load cycles.
Signs that an engine is nearing rebuild include:

• Excessive blow-by from the crankcase breather
  
• Blue or black exhaust smoke under load
  
• Oil consumption exceeding 1 quart per 10 hours
  
• Knocking sounds during cold starts
  
• Low oil pressure at idle (below 20 psi)
  

If the engine starts easily, maintains stable oil pressure, and shows no signs of smoking or knocking, it may still have usable life. Nonetheless, buyers should budget for a rebuild, which typically costs $12,000–$15,000 depending on labor rates and parts availability.
Oil Analysis and Preventative Diagnostics
Before purchasing a high-hour grader, oil analysis is strongly recommended. This process involves sending a sample of engine oil to a lab to test for:

• Metal particles (iron, aluminum, copper)
  
• Fuel dilution
  
• Coolant contamination
  
• Viscosity breakdown
  

Oil analysis can reveal internal wear long before symptoms appear. It’s a standard practice among fleet managers and offers peace of mind when evaluating older machines.
In one case, a county highway department in Minnesota extended the life of a 770BH grader to 17,000 hours by performing regular oil analysis and replacing injectors and valve seals proactively. The original engine remained in service with only minor head work.
Transmission Rebuilds and Component Sourcing
The 670B’s powershift transmission is robust but not immune to wear. A factory-reconditioned transmission adds value to a used machine, especially if installed by a certified technician. Common failure points include:

• Clutch pack wear
  
• Valve body sticking
  
• Torque converter slippage
  
• Ring and pinion degradation
  

If sourcing a remanufactured transmission proves difficult, rebuild kits are available through aftermarket suppliers. Unless the ring and pinion are damaged, most transmission shops can rebuild the unit for $6,000–$8,000. Replacing the torque converter and flushing the cooling system during rebuild is recommended to prevent overheating and premature failure.
Hydraulic System and Leak Management
A mostly leak-free hydraulic system on a 670B is a good sign, especially considering the age. Deere’s hydraulic circuits are modular and relatively easy to service. Common leak points include:

• Hose fittings and couplers
  
• Control valve seals
  
• Cylinder rod seals
  
• Pump shaft seals
  

Preventative steps include:

• Replacing hoses every 5–7 years regardless of condition
  
• Using UV dye to trace slow leaks
  
• Installing hydraulic breathers to reduce moisture ingress
  
• Flushing fluid every 2,000 hours or annually
  

A grader operating in dusty or humid environments may require more frequent service. In Ohio, a retired operator reported that his 670B’s hydraulics remained tight for over a decade with regular filter changes and fluid sampling.
Cooling System and Radiator Maintenance
Cooling system neglect is a leading cause of engine failure in older graders. Boiling out the radiator—an industrial cleaning process that removes scale and sediment—is essential during engine rebuilds. A clogged radiator can reduce cooling efficiency by 30% or more, leading to overheating under load.
Recommendations:

• Pressure test the radiator and cap annually
  
• Replace coolant every 1,000 hours or two years
  
• Inspect fan belts and shrouds for wear
  
• Upgrade to high-efficiency cores if operating in hot climates
  

In South Dakota, a sales consultant noted that a neglected cooling system added $2,000 to a rebuild due to warped cylinder heads and cracked liners.
Conclusion
The John Deere 670B motor grader remains a viable machine even at 12,000 hours, provided it has been well maintained and inspected thoroughly. While the engine may be nearing the end of its service life, a rebuild is a predictable investment for a machine of this vintage. With a reconditioned transmission, solid tires, and a clean hydraulic system, the 670B can continue grading for years to come. Buyers should approach the purchase with realistic expectations, budget for future repairs, and use oil analysis and visual inspection to guide their decision. In the world of heavy equipment, longevity is earned through care—and the 670B has proven it can go the distance.