Replacing Drive Motor Seals on a Mustang 2086 Skid Steer

[MikePhua]

The Mustang 2086 and Its Hydraulic Drive System
The Mustang 2086 skid steer loader was introduced in the early 2000s by Mustang Manufacturing, a company with roots dating back to 1865. Known for producing compact equipment with robust hydraulic systems, Mustang gained traction in the North American market through its focus on operator comfort, serviceability, and affordability. The 2086 model featured a rated operating capacity of around 2,000 lbs, a turbocharged diesel engine producing approximately 80 horsepower, and a hydrostatic drive system that powered each side independently through hydraulic motors.
These drive motors are critical to the machine’s maneuverability and torque delivery. Each motor is mounted directly to the chain case, which transfers rotational force to the wheels via roller chains. The integrity of the motor seals is essential to prevent hydraulic fluid from leaking into the chain case and to maintain pressure balance across the system.
Terminology annotation:
- Hydrostatic Drive: A propulsion system using hydraulic fluid to transfer power from the engine to the wheels or tracks. - Chain Case: An enclosed compartment housing roller chains that transmit drive motor output to the wheels. - Drive Motor Seal: A gasket or lip seal that prevents hydraulic fluid from escaping the motor housing and contaminating adjacent components.
Symptoms of Seal Failure and Chain Case Pressurization
One of the most common signs of drive motor seal failure is oil seepage around the chain case cover plate. In some cases, the chain case begins to pressurize, forcing hydraulic fluid into areas it shouldn’t be. This can lead to overfilling, pressure buildup, and eventual leakage from the fill plug or cover gasket.
Operators may notice:

• Hydraulic oil pooling near the chain case
  
• Pressure release when removing the fill plug
  
• Uneven fluid levels between left and right chain cases
  
• Reduced drive performance or erratic movement
  

In the Mustang 2086, the absence of chain case vents exacerbates the issue. Without a pressure relief mechanism, any fluid intrusion from the drive motor accumulates and forces its way out through seals or gaskets.
Terminology annotation:
- Vent Port: A small opening designed to equalize pressure within a sealed compartment. - Fill Plug: A threaded cap used to add or inspect fluid levels in a reservoir or case. - Seepage: A slow leak of fluid through a compromised seal or gasket, often appearing as residue or staining.
Repair Procedure and Accessibility
Replacing the drive motor seals is a manageable task once the motor is removed from the machine. On the Mustang 2086, the motor can be accessed without dismantling major components, though clearance is tight. The motor itself weighs approximately 60–80 lbs, making it liftable by a single technician, though a cherry picker or engine hoist may be used for safety.
Steps for seal replacement:

• Disconnect hydraulic lines and cap them to prevent contamination
  
• Remove mounting bolts and lift the motor from the chain case
  
• Clean the motor exterior and inspect for scoring or wear
  
• Disassemble the motor housing to access the seal cavity
  
• Replace seals using OEM or high-quality aftermarket kits
  
• Reassemble and torque bolts to specification
  
• Reinstall motor and refill chain case with appropriate lubricant
  

Terminology annotation:
- Scoring: Surface damage caused by friction or debris, often visible as grooves or scratches. - OEM Kit: A seal replacement set produced by the original equipment manufacturer, ensuring compatibility and durability. - Torque Specification: The recommended tightness for bolts, measured in foot-pounds or Newton-meters, to prevent over-tightening or loosening.
One technician noted that hydraulic oil rated AW46 (Anti-Wear 46) does not harm the chains and can be used temporarily in the chain case. In fact, some operators reuse drained hydraulic fluid for chain lubrication, though this practice should be limited to clean, filtered oil.
Preventative Measures and Chain Case Maintenance
To prevent future seal failures and chain case pressurization:

• Install vent ports or breather caps on chain cases if not factory-equipped
  
• Monitor fluid levels weekly and inspect for cross-contamination
  
• Replace seals proactively during major service intervals
  
• Use high-quality hydraulic fluid with anti-foaming and anti-wear additives
  
• Avoid overfilling the chain case, which can increase internal pressure
  

Terminology annotation:
- Breather Cap: A vented cap that allows air exchange while preventing debris ingress. - Anti-Foaming Additive: A chemical agent that reduces air bubble formation in hydraulic fluid, improving system performance. - Cross-Contamination: The mixing of fluids from separate systems, often leading to performance degradation or component damage.
One operator shared that after installing vent ports and switching to synthetic hydraulic fluid, his Mustang 2086 ran cooler and showed no signs of chain case pressurization for over a year. Another technician added a sight gauge to monitor fluid levels without removing the fill plug, improving inspection efficiency.
Conclusion
Drive motor seal failure in skid steers like the Mustang 2086 is a common but solvable issue. With proper diagnosis, careful disassembly, and quality replacement parts, operators can restore full function and prevent chain case contamination. Adding venting, monitoring fluid levels, and using compatible lubricants are key to long-term reliability. In compact equipment, even small seals play a big role—and every drop of oil tells a story of pressure, wear, and resilience.