Bosch Rexroth A2FM fixed displacement motor for Caterpillar excavator 152-7371 171-1881 1772342 160-0198-01 242-4042-02 296-7684-04 368-2782-01

The A2FM is a fixed displacement axial piston motor built in a bent-axis configuration, designed by Bosch Rexroth for hydrostatic drive systems in both open and closed hydraulic circuits. Unlike a variable displacement motor, its swept volume never changes — the output speed and torque are dictated purely by the flow and pressure differential coming from the pump, which makes it a simple, predictable, and mechanically rugged choice for demanding mobile equipment.

In the bent-axis design, the pistons sit at an angle (commonly around 40°) relative to the drive shaft rather than parallel to it, as you'd see in a swash-plate motor. The pistons bear directly against the drive shaft flange, and pressurized fluid acting on the pistons generates torque proportional to the pressure differential between the inlet and outlet ports. This layout is inherently stout: fewer wear-prone components, high starting efficiency even under load, and strong resistance to contamination and shock loading — all traits that matter on a machine that spends its life on a jobsite rather than a showroom floor.

Where the A2FM Fits on a Caterpillar Excavator

Caterpillar excavators rely on hydrostatic circuits for two motion-critical functions: track travel and swing (slew) rotation. Both are natural homes for a fixed displacement bent-axis motor like the A2FM.

Travel (Track) Drive Application

On the travel side, the A2FM converts pump flow into the torque that turns the final drive and sprocket, propelling the excavator forward or backward. Because travel motors deal with constant shock loading from uneven ground, high-cycle direction reversals, and long periods under full pressure, the bent-axis motor's simple rotary group and robust bearing arrangement hold up well compared to motors with more moving control components.

Swing (Slew) Drive Application

The swing circuit is arguably an even tougher duty. Every time an operator swings the house to dump a bucket, the motor accelerates, decelerates, and often reverses — sometimes dozens of times per hour, all day, every day. A2FM-family motors used here are frequently paired with a counterbalance valve to manage overrun during deceleration and to hold the upper structure in place on a slope without drift.

Common Failure Signs to Watch For

If you're troubleshooting a Cat excavator with a suspected A2FM issue on the travel or swing circuit, watch for:

Grinding or whining noise during rotation, especially under load

Excessive shaft play at the coupling or sprocket

Erratic swing or travel speed despite steady lever input

Milky or foamy case-drain oil, a classic sign of seal failure, allowing water or air ingress

Rising hydraulic oil temperature at idle, which can point to internal bypass and declining volumetric efficiency

Catching these early usually means the difference between a seal kit and a full rotary group replacement.

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Q1: How do I know what size A2FM I need for my excavator?

A1: Match the motor's displacement to your machine's pump flow, target speed, and required torque at your system's nominal operating pressure. The safest approach is to pull the original part number from the failed motor's nameplate or your Cat parts catalog and cross-reference it with a Rexroth or supplier parts specialist rather than guessing from displacement alone.

Q2: How long does an A2FM motor typically last on an excavator?

A2: Service life depends heavily on fluid cleanliness, operating pressure, and duty cycle, but a well-maintained unit with clean hydraulic fluid and no history of cavitation or contamination commonly runs for several thousand hours before internal wear becomes noticeable. Regular case-drain oil analysis is the best early-warning tool.

Q3:What is the price and delivery time of the Rexroth A2FM motor for the Caterpillar excavator？

A3: The specific price and delivery time will depend on the equipment model or specific product model you provide.

Q4:How to purchase a Rexroth A2FM motor for the Caterpillar excavator?

A4:You can visit https://www.baolilaihydraulic.com/contact/ to contact us and purchase our products through various methods.