Case 850G Transmission Inquiry

[MikePhua]

Introduction
The Case 850G is a crawler dozer (or crawler tractor) that has been used in construction and agricultural contexts. Its drive and transmission system are integral to its function under load. While public documentation is limited, operator discussions along with known specifications offer insight into how the transmission behaves, common issues, and maintenance practices. Below is a synthesized, detailed analysis based on machine specs and community experience.
Machine Context and Specifications
The 850G is part of the line of crawler tractors/dozers built by Case. According to published sources, the machine has the following key specs:

• It uses a Case 6T-590 six-cylinder diesel engine.
  
• Gross power is around 133 horsepower; net power about 119 hp.
  
• The machine features 4 forward gears and 4 reverse gears.
  
• Top speeds are about 5.6 mph forward and 6.1 mph reverse in crawler mode.
  
• Operating weights, hydraulic system parameters, and other specs vary by configuration.
  

Given this baseline, the transmission works in concert with the engine, torque converter, and final drives to deliver power to the tracks.
Operator Observations and Concerns
From user discussions and practical experience, a few recurring themes emerge about the 850G’s transmission behavior:

• Fluid Type Sensitivity: Many operators stress that the transmission and torque converter use a specialized fluid (often called “TCH” by Case users) and that using alternate fluids—like general-purpose hydraulic oils such as Hytran—can damage internal clutch linings over time. Using the correct fluid is critical for clutch life and smooth operation.
  
• Shifting Under Load: On slopes or during heavy pushing work, abrupt shifts between forward and reverse can place stress on the driveline. Some operators recommend idling down before shifting, applying brakes, then reaccelerating to reduce shock to components.
  
• Brake-Transmission Interaction: The dozer’s braking system may interact with the transmission’s neutral or power cutoff under certain operations. Some operators mention a knob or setting that determines whether applying brakes cuts track power (i.e., shifts toward neutral) or maintains track movement under braking.
  
• Fluid Capacities and Fill Points: Operators have made rough estimates for fluid volumes:
   – Transmission + torque converter combined: ~8 gallons (for some 850 variants)
   – Final drives: behavior akin to gear oil in each side
   – Engine and hydraulic systems will have separate capacities
  These estimates come from user restorations and aftermarket spec gathering and may vary by sub-model (e.g., 850 vs 850C/G).
  
• Maintenance Best Practices: Upon acquiring an older machine, many recommend replacing all transmission, torque converter, hydraulic, engine oils and filters before undertaking heavy work. Checking for leaks, inspecting screens or strainers in the torque circuit, and cleaning belly pans are common advice.
  

Analysis of Transmission Design
Given the machine’s era and architecture, the transmission design likely includes:

• A torque converter (fluid coupling) between engine and transmission to allow smooth power transfer and torque multiplication.
  
• A multi-gear planetary or power shift gearbox (4 forward, 4 reverse) allowing different speed ranges.
  
• Wet clutches inside the transmission (hence sensitivity to correct fluid) that engage/disengage gear sets.
  
• Interfacing with the brake and track steering system so that braking or track hold commands can affect power delivery to the tracks.
  

Because it’s a crawler machine, the transmission must operate under high load, low-speed heavy torque conditions. That increases stress on clutch packs and fluid shearing, so fluid quality, cooling, and maintenance are even more critical than in road vehicles.
Solutions and Recommendations
To address transmission issues and ensure longevity, consider the following:

• Confirm fluid specs: Obtain the correct Case service manual or parts documentation to verify the specified transmission/torque converter fluid (often referred to as “TCH” in Case circles). Do not substitute general hydraulic fluid unless confirmed safe by documentation.
  
• Use gradual shifting techniques: On slopes or heavy loads, reduce engine rpm to idle before shifting direction, allow the system to stabilize, then increase throttle. Avoid abrupt direction changes under load.
  
• Maintain brake–transmission settings: Understand and use the brake knob or setting that determines whether braking cuts track power or holds torque flow—adjust as per job conditions.
  
• Routine inspections: Check for leaks, inspect internal screens or filters in the torque circuit, clean any debris from sumps or belly plates, and ensure cooling systems are functioning to prevent overheating of fluid.
  
• Fluid replacement schedule: Use a conservative schedule for replacing transmission and torque converter fluid, especially in machines of higher hours or heavy usage.
  
• Parts matching by serial/model: Because design variations may exist (e.g., between 850, 850C, and 850G), always match parts and fluid specs based on serial number or model variant to avoid incompatibility.
  

Conclusion
While the Case 850G is not a widely documented machine in modern catalogs, combining published specifications with field operator experience provides a useful picture of its transmission system and potential weak points. The transmission is built to handle heavy torque and slow speeds, making fluid choice, smooth shifting, and preventative maintenance the keys to reliable operation. Operators who respect these factors can continue to use aging machines like the 850G with confidence for years.