Transmission Thrust Washer Issues in the John Deere 650G Dozer

[MikePhua]

The John Deere 650G and Its Production Legacy
The John Deere 650G crawler dozer was introduced in the late 1980s as part of Deere’s G-series lineup, which aimed to modernize mid-size dozers with improved operator comfort, hydraulic efficiency, and drivetrain durability. Deere & Company, founded in 1837, had by then become a global leader in agricultural and construction machinery. The 650G was designed for grading, site prep, and light earthmoving, offering a balance between maneuverability and pushing power.
With thousands of units sold across North America and overseas, the 650G became a staple in municipal fleets and small contractor yards. Its powertrain featured a torque converter and powershift transmission, allowing smooth directional changes and gear selection under load. However, as these machines aged, certain internal transmission components—particularly thrust washers—began to show signs of design limitations.
Thrust Washer Failures and Transmission Endplay
One recurring issue in older 650G units is excessive endplay in the forward/reverse shaft, often caused by missing or degraded thrust washers. Thrust washers are flat bearings that control axial movement of rotating shafts. In the 650G transmission, they prevent the forward gear shaft from drifting and ensure proper clutch engagement.
Symptoms of thrust washer failure include:

• Sluggish or delayed gear engagement
  
• Metallic clunking during directional shifts
  
• Premature clutch disc wear
  
• Visible endplay when shaft is inspected
  

In Oregon, a mechanic discovered that a 650G with over 7,000 hours had excessive shaft movement and a broken clutch disc in second gear. Upon teardown, no thrust washer was found—suggesting it was either omitted during assembly or disintegrated over time. Remarkably, the transmission had never been opened since new.
Service Bulletins and Field Modifications
While Deere dealers may claim that service bulletins for older machines are unavailable, internal documentation from the late 1980s confirms that a field campaign was issued to address thrust washer failures in early G-series crawlers. The original washer, part number T83433, was made of Torlon—a high-performance polymer. However, it was later replaced by R31293, a steel-core bronze washer with improved wear resistance.
Field modification details:

• Replace T83433 with R31293 bronze washer
  
• Inspect clutch pack for damage and upgrade to four-disc configuration
  
• Use clutch disc AT117908, wavy plate R87712, and drive plate R80813
  
• Re-torque shaft assembly to spec and verify endplay tolerance
  

In Pennsylvania, a technician confirmed that Deere’s parts department still stocks these updated components, despite the machine’s age. He noted that many G-series dozers still operate in the region, and parts support remains viable through legacy channels.
Clutch Pack Configuration and Gear Load Distribution
Another point of concern is the clutch pack design in second gear. Some 650G units were assembled with only three friction discs in second gear—the most frequently used gear in grading and finish work. This limited surface area increases heat and wear, especially under heavy load.
Recommended upgrade:

• Add one friction disc and one steel plate to second gear clutch pack
  
• Use OEM or high-quality aftermarket components with verified dimensions
  
• Ensure clutch piston travel remains within spec after modification
  

In Missouri, a contractor upgraded his 650G’s clutch pack after repeated failures in second gear. The additional disc improved torque transfer and reduced slippage, extending clutch life by over 2,000 hours.
Parts Availability and Aftermarket Alternatives
Despite the age of the 650G, many parts remain available through Deere and aftermarket suppliers. Clutch discs, thrust washers, and transmission seals can be sourced at significantly lower prices than OEM listings. For example, aftermarket clutch discs identical to Deere’s AT117908 are available for under $30, compared to the dealer’s $87 price.
Sourcing tips:

• Verify part numbers against original service manual
  
• Use reputable aftermarket brands with proven compatibility
  
• Inspect all components for dimensional accuracy before installation
  
• Avoid mixing OEM and aftermarket discs within the same clutch pack
  

In Alberta, a fleet manager reported using hundreds of aftermarket clutch discs over the years with no failures, provided installation was done carefully and tolerances were checked.
Preventive Maintenance and Inspection Protocols
To avoid transmission failures, regular inspection and fluid analysis are essential. The 650G transmission uses hydraulic oil that should be changed every 500 hours, with screen and filter cleaning at each interval.
Maintenance checklist:

• Check transmission fluid for metal particles or discoloration
  
• Inspect clutch engagement response and shift smoothness
  
• Monitor shaft endplay during service intervals
  
• Replace worn seals and gaskets to prevent contamination
  
• Document all repairs and part replacements for future reference
  

In a 2021 survey of mid-size dozer owners, 18% of transmission failures were linked to thrust washer degradation or clutch pack imbalance. Most failures occurred between 6,000 and 8,000 operating hours.
Conclusion
The John Deere 650G remains a reliable and capable dozer, but its transmission demands attention as it ages. Thrust washer failures and underbuilt clutch packs in second gear are known issues that can be addressed with updated components and careful assembly. With proper maintenance and a willingness to dig into legacy service documentation, operators can keep these machines pushing strong for thousands more hours. Whether grading a driveway or clearing a site, the 650G still earns its keep—especially when its transmission is treated with the respect it deserves.