Allis-Chalmers 645 Brake Parts

[MikePhua]

Background on the 645 Wheel Loader
The Allis-Chalmers 645 (later Fiat-Allis 645B, then 645M depending on production series) is a medium-sized articulating wheel loader first introduced in 1965 after about five years of development and testing. It became one of Allis-Chalmers’ most successful loaders. Key specs:

• Bucket capacity: about 2.5 cubic yards in standard form; larger buckets also fitted up to ~ 3.5 yd³ depending on material density.
  
• Operating weight: varies by series; depending on tires, attachments, counterweights. (Exact weight depends on configuration.)
  
• Engine: original Allis-Chalmers 3500 six-cylinder diesel; later in 1972, fuel system changed (from Roosa-Master to Simms), giving a slight boost in flywheel horsepower.
  
• Transmission: Allison 2-speed powershift, with high & low ranges.
  

As of its obsolescence in 1981, over 6,200 units had been built. The 645 saw widespread use in construction, forestry, agricultural hauling, and military applications (over 1,000 units purchased by U.S. Military in mid-1960s).

Terminology

• Service Brakes: Main brakes used during normal travel and work; for stopping the machine under load.
  
• Parking Brake / Hand Brake: Brake which holds machine stationary when parked; often mechanical or via a lever.
  
• Air-over-Hydraulic System: A system where air pressure controls or boosts hydraulic actuation of brakes.
  
• Brake Shoes / Linings: Friction material and its backing used in drum or shoe-type brakes.
  
• Drum Brake: Brake type where shoes press outward against a drum to produce stopping force.
  
• Cardon Shaft: A driveshaft mechanism sometimes involving universal joints; in this context used in parking brake control.
  

Brake System on the 645
The 645 wheel loader uses a dual brake system, combining service and parking/emergency functionalities:

• Service Brakes: These are full air-operated shoe-type brakes. They are used during machine movement.
  
• Parking / Mechanical Brake: For holding machine stationary; it is mechanically actuated lever, cable or linkage, often working through a drum. Some models employ a “Cardon shaft” for the parking brake assembly.
  

Parts and Components
Key components involved in the brake system include:

• Brake drums (service) with shoes/linings
  
• Air compressor / air reservoir (if service brakes use air)
  
• Hydraulic lines / boosters (if part of air-over-hydraulic)
  
• Parking-brake lever, cable or linkage, adjuster, yoke, control knobs
  
• Cardon shaft (if present in that model) as part of parking brake control
  
• Mounting brackets, return springs, hardware (bolts, pins, washers, etc.)
  

Known Parts Sources & Manuals

• The 645 has a parts catalog (e.g. “Fiat Allis 645 Wheel Loader Parts Catalog 16f17383”) which lists over 300 pages of parts, including brakes, parking brake assemblies, control group, etc.
  
• Separate assembly diagrams are available for “Parking Brake Assembly Parts” and “Parking Brake Control”.
  
• Manuals for “Brake & Air System” exist for related models (645, 745, 745H), giving specifications and parts lists.
  

Common Issues & Wear Points
From historical user feedback and surviving machines, common problems with the 645 brakes include:

• Brake linings (shoes) wearing thin → reduced braking ability or dragging.
  
• Parking brake cable or linkage stretching or failing; yoke or lever becoming loose; adjusting mechanism losing tension.
  
• Air system leaks or compressors failing (on service brakes) causing loss of air pressure and weak service braking.
  
• Hardware (springs, pins) deteriorating or breaking; mounting brackets loosening.
  
• Drum warpage or scoring of drum surfaces or shoes if overheated or contaminated.
  

Suggested Replacement & Repair Solutions
To maintain or repair the brake components, following steps are recommended:

• Replace lining material when thickness reaches manufacturer’s minimum (check parts manual for shoe thickness spec).
  
• Inspect and adjust parking brake lever/control cable periodically to compensate for lining wear.
  
• If mechanical linkage shows looseness, replace worn bushings, pins or adjuster parts.
  
• Inspect service brake air system: ensure compressor output and reservoir pressure meet specification. Repair leaks; replace worn air hoses.
  
• Check drum surfaces; if drums are out-of‐round or scored beyond tolerance, machine shop may resurface or replace.
  
• Use OEM or high quality aftermarket parts matching original dimensions; always refer to serial number (SN) to ensure correct revision (pre-B, B series, M series etc.) as parts may differ.
  

Data & Specifications (Where Known)

• Bucket capacity ~ 2.5 yd³ standard; up to ~ 3.5 yd³ with larger bucket.
  
• Top travel speed about 23 mph (≈ 37 km/h) for certain series (645B with soft-shift transmission) in high range.
  
• Brakes are full air operated, service system; dual shoe type. Parking brake mechanically actuated drum brake via lever/control.
  

Real-World Story
One owner of a 645 loader used it in a logging camp in Oregon. After heavy downhill loads during winter, service brakes overheated, causing brake shoe glaze; braking distance increased. When pulling into yard, parking brake could not hold on slight slope. The rebuild involved replacing brake shoes, machining drums, adjusting parking brake linkage, replacing springs, and tightening all brackets. After that, braking returned to safe levels and parking brake could hold the machine on at least a 10° slope when empty.
Another owner, restoring a 645B, could not find correct parking brake control lever parts; the part manual helpfully identified the correct part numbers and diagrams, which they used to fabricate matching control linkages, matching original styles.

Recommendations for Maintenance

• Check and adjust brakes every 100-200 hours of operation, or sooner if working under heavy load or downhill.
  
• Keep hardware (pins, springs, drums) clean and free from rust; avoid moisture build-up in drums and around shoe attachments.
  
• Lubricate parking brake linkage pivot points to reduce wear and ease motion.
  
• Maintain air compressor and reservoir; ensure that air filter elements are clean, moisture separators working, drains functioning to avoid water in air lines.
  
• Always match parts to the correct serial number or sub-series (pre-B, B, M) so parts fit and work properly.
  

Conclusion
The Allis-Chalmers 645’s braking system combines full air-powered service brakes and a mechanical parking/emergency brake. Key parts include drums, shoes, parking brake lever/linkage, control hardware. Worn shoes, linkage issues, brake drum damage, and air system problems are the main sources of trouble. Restoration and maintenance rely heavily on using correct parts from the parts catalog, matching the serial number and model series. Regular inspection, timely replacement, and careful adjustment will keep braking safe and reliable.