Need Help with Case 850D Longtrack

[MikePhua]

Overview of the Case 850D
The Case 850D is a crawler (tracked) dozer made by Case (later Case Corporation / Case Construction), built roughly in the 1980s–early 1990s. It uses a Cummins 6-590 or 6T-590 diesel engine, putting out about 82 net horsepower (≈90 gross HP).  The machine weighs around 17,158 lbs (≈7,785 kg), with operating dimensions of about 13 ft 1 in long, 8 ft 6 in wide, and 8 ft 10 in high.  It has a power-shift transmission, 4 forward and 4 reverse speeds in many spec sheets.
Built to be rugged and reliable for grading, push work, etc., the 850D has a following among farmers, landowners, and contractors who value simplicity and parts availability. Common attachments include 6-way blade setups, and “long track” variants give better ground contact (better flotation, less ground pressure) useful on soft or uneven ground.
What to Check Before Buying / Testing
If you’re looking at purchasing one or putting a used 850D through its paces, especially a “Longtrack” version (longer tracks / longer undercarriage), here are tests and inspections to perform, direct from operator experience and common problem areas.

• Battery / Electrical System — Check battery condition and voltage. Corrosion on terminals, or rodents chewing wiring under the dash are surprisingly common issues. Pull back panels and inspect wiring where it enters control levers or pedal stations.
  
• Safety Levers / Controls in Neutral — Many owners report that the unit will not start, or starter push buttons do nothing, when safety interlocks aren’t engaged. Make sure that the steering/gearing levers are in neutral.
  
• Throttle / Engine Run Test — Set throttle mid-range (to allow some revs but not wide open) when testing. Listen for smoke, odd noises, check oil pressure, leaks. A machine that “runs strong with no hesitation,” clean exhaust and good oil pressure is a big plus.
  
• Transmission / Drivetrain Movement — After starting, test forward and reverse. Pay attention if the machine feels like it’s in neutral when you expect torque. It may be sluggish when cold, or the hydraulic / transmission fluid may be low or have been poorly maintained.
  
• Undercarriage Condition — Check track shoes (pads), rollers, idlers, sprockets. Look for:
  • Roller looseness (“sloppy rollers”) or worn bearings.
  • Tracks that are too loose or too tight.
  • Sprocket wear (flat spots, worn peaks or ‘valleys’) and bushing shape (ovalizing = “egg-shaped”).
  
• Brakes / Turning Ability — Many “850” operators warn that the braking / turning system (including master and slave cylinders, hydraulic or pneumatic depending on configuration) tends to be weaker or a problem point. Test turning in both directions; notice hesitancy, slipping, or difference between right and left tracks. Check for fluid leaks.
  
• Transmission Warm-Up Behavior — Some machines will not move until the transmission / fluids warm up. Cold weather or cold fluids can reduce hydraulic or hydraulic-related driveline performance. If it runs poorly until warm, that may indicate filters (suction, safety, bypass filters) are dirty or partially blocked.
  
• Master / Dowel Pins in Track Chain — The “longtrack” versions sometimes use master pin or ‘alligator’ (bolt-on pad) track links. These require inspection for correct assembly, whether master pins are in place, whether track links are reversed or incorrectly installed. A mis-installed or backward pin can cause issues, especially when taking the track apart for maintenance.
  

Common Problems and Fixes
Based on reports from owners and mechanics, here are recurring issues and how people have remedied them:

• “Machine won’t move / feels neutral” — Causes include low transmission fluid, cold/hardened fluid, blocked filters, stuck modulator valve spool. One owner disassembled the modulater valve, cleaned it, polished the bore and spool with fine grade paper, reassembled, and got normal movement restored.
  
• Uneven turning or one side weak — Could be brake fluid loss, master or slave cylinder issues, hydraulic leaks. Inspect each side individually, check pedal response, and check the linkage to the braking or steering clutches.
  
• Sloppy or noisy undercarriage components — Rollers, idlers, bushings wear with time. Replacing worn rollers / bearings, replacing pad bolts, adjusting chain tension can lengthen life.
  
• Track separation / idler issues — Front idlers may get hot, noise may develop (dragging drag-braake-like sound), resistance in turning or moving. Depending on condition, some choose to replace the whole idler assembly rather than individual bearings, especially on older machines where sealing and alignment may be compromised. Master pin or alligator style track links factor into whether track separation tools are needed.
  

Step-By-Step Test Drive / Inspection Guide (“For Dummies” Test Sequence)
Here’s a logical sequence for evaluating a Case 850D before buying or committing to heavy use. Estimate for a used unit: allow 1-2 hours minimum, more if undercarriage is included.

1. Pre-Start Visual Check
   • Inspect battery, fluid levels (engine oil, coolant, transmission and hydraulic fluid)
     
   • Look for leaks, rust, broken or loose components
     
2. Electrical / Ignition Check
   • Key “on” – check for dash lights, indicators
     
   • Ensure safety levers / neutral locks are in the proper positions
     
3. Start Engine
   • Let idle, check for smooth running, smoke check, listen for knocking or rattling
     
   • Warm-up sufficiently to operating temperature
     
4. Transmission / Movement Test
   • Drive forward / reverse, test stationary turning (using hi-low range or torque convertor input)
     
   • Note lag, slipping, strange sounds
     
5. Blade / Attachment Check
   • If a 6-way blade is installed, test lift, tilt, side shift, look for leaks in blade cylinders
     
6. Undercarriage Inspection while Moving
   • Observe track tension, ride quality, sound of idlers, rollers
     
7. Brake / Turn Responsiveness
   • Test turning both directions under low and moderate speeds
     
8. After Shutdown
   • While engine is still warm, check fluid sampling (engine oil, transmission oil may show metallic particles)
     
   • Inspect undercarriage for wear revealed under load
     

Maintenance Intervals & Specs
Some relevant data and intervals to help you plan upkeep:

• Change engine oil & filter every 200-300 hours under normal use; under harsh conditions maybe every 200.
  
• Transmission & final drive fluids: consider changing every 500 hours (depending on use and condition).
  
• Track & roller grease / lubrication: weekly or every work shift depending on mud/sand exposure.
  
• Cooling system: flush annually or more often if in dusty or dirty conditions.
  

Operational specs recap:

• Net power ~ 82 HP at ~2,000 rpm.
  
• Max torque ~ 253 lb-ft at ~1,500 rpm.
  
• Fuel capacity ~ 40 gallons.
  

Anecdotes and Real-World Lessons

• One owner related that after sitting overnight in cold weather, their 850D would not move at all until warmed up for 10-15 minutes. The culprit turned out to be a clogged suction screen in the transmission pump. Once cleared, even cold starts moved almost immediately.
  
• Another recounts that uneven braking (strong on one side, weak on the other) caused by a failed slave cylinder led to poor turning. Fixing that allowed much better maneuverability, especially on slopes.
  
• In a sale listing, an 1987 Case 850D with about 4,420 hours and open-cab, with “only ~50 hours on the undercarriage since overhaul,” was priced around US$35,000. Machine condition graded fairly high (4/5) and included Berco oil-filled track chains. This shows the potential value of units with rebuilt or minimally worn undercarriage.
  

Summary Advice
If you’re considering acquiring a Case 850D Longtrack or already own one:

• Check that engine, transmission, and undercarriage are sound before making major investment.
  
• Factor in the cost of undercarriage wear: track shoes, rollers and idlers tend to be among the costliest items.
  
• Know how to operate the specialized controls (high/low range levers, forward/reverse, foot pedals) to avoid damaging parts by misuse.
  
• Make sure any dozer you buy has been properly maintained: filtration, fluid condition, cooling systems.