Restoring the Volvo 846 BL Wheel Loader and Understanding Its Z-Linkage Heritage

[MikePhua]

Volvo BM’s Mid-Size Loader Evolution
The Volvo 846 BL, often referred to as part of the BL/BM lineage, represents a transitional phase in Volvo’s wheel loader development during the 1970s and early 1980s. Built under the Volvo BM brand before the full integration into Volvo Construction Equipment, the 846 BL was designed for mid-size earthmoving tasks, quarry work, and municipal operations. It featured a robust frame, mechanical simplicity, and a Z-linkage boom system that distinguished it from earlier parallel-arm designs.
Volvo BM’s loader series included models like the LM 641, LM 840, LM 1240, and LM 1640, each evolving in hydraulic sophistication and operator comfort. The 846 BL was notable for its adoption of the Z-bar linkage, a configuration that improves breakout force and bucket rollback angles—especially useful in dense material loading.
Z-Linkage Versus Parallel Linkage
The Z-linkage boom design uses a single lift arm with a bell crank and connecting rods to control bucket movement. This contrasts with parallel linkage systems, which maintain consistent bucket orientation throughout the lift cycle—ideal for pallet handling and precise placement.
Advantages of Z-linkage include:

• Higher breakout force at ground level
  
• Better visibility due to simplified arm geometry
  
• Fewer pivot points, reducing wear
  
• Enhanced digging performance in compacted soil
  

Volvo continued offering both linkage types in later models, such as the L50 and L70, allowing customers to choose based on application needs.
Challenges in Restoration and Parts Availability
Restoring an old Volvo 846 BL presents several mechanical and logistical hurdles:

• Center pin wear: A common issue in articulated loaders, where the pivot between front and rear frames becomes loose. Repair requires splitting the machine and machining or replacing bushings and pins.
  
• Hydraulic line routing: Some owners consider reversing steering arm hoses to manipulate frame alignment during disassembly.
  
• Obsolete parts: Many components, especially electrical and hydraulic fittings, are no longer stocked by dealers. Aftermarket suppliers or salvage yards may offer limited support.
  

One owner in the UK described his 1976 846 BL as “in a sorry state,” with significant wear in the articulation joint. He planned to anchor the front half with the bucket and support the rear frame to prevent tipping during repair—a method consistent with industry practice.
Operational Characteristics and Performance Notes
When properly maintained, the Volvo 846 BL offers:

• Operating weight around 10,000–12,000 kg
  
• Bucket capacity of 1.5–2.0 cubic meters
  
• Mechanical transmission with torque converter
  
• Hydraulic system pressure near 200 bar
  

The loader’s performance is comparable to machines like the Michigan 55A, though the Volvo’s Z-linkage gives it an edge in breakout force. Operators appreciate its straightforward controls and visibility, though cab ergonomics lag behind modern standards.
Preserving Volvo’s Industrial Heritage
Volvo BM loaders like the 846 BL are part of a broader legacy that shaped European construction equipment. Their rugged design and mechanical reliability made them popular in Italy, Scandinavia, and the UK. Enthusiasts restoring these machines contribute to preserving industrial history, often fabricating parts or adapting components from newer models.
For those seeking similar machines with Z-linkage, the following models are worth exploring:

• Volvo L50 and L70 (early versions)
  
• BM 4500 and BM 1641
  
• LM 70 and LM 80 series
  

Each offers variations in linkage geometry, hydraulic layout, and frame articulation.
Conclusion
The Volvo 846 BL is more than an old loader—it’s a symbol of Volvo BM’s engineering philosophy during a pivotal era. With its Z-linkage boom, durable frame, and mechanical simplicity, it remains a viable candidate for restoration and light-duty use. While parts may be scarce, the knowledge shared among operators and mechanics ensures that these machines continue to move earth—and memories—for years to come.