Master the electronics of your 4WD loader with the **John Deere 644J Operation and Test Manual (TM10231)** from **Texas Manuals**. Essential for identifying failures on SN 611232+ units before they lead to project delays.
### **Technical Data:**
* **Drivetrain Diagnostics:** Specialized troubleshooting for powershift transmissions and axles.
* **Electrical Maps:** Full machine wiring diagrams for rapid circuit troubleshooting.
* **Operational Checkout:** Systematic verification to ensure factory standards are met.
* **Pressure Specs:** Official John Deere benchmarks for main pump and steering circuits.
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