John Deere 544E, 624E, 644E Repair Manual (incl. Wiring)

Check hydraulic fluid level first, then release residual pressure by cycling the loader control valve, brake valve, and steering valve as described on page 68. Inspect the gear-type pump for wear — the rear cover cap screws torque to 271 N·m (200 lb-ft) per page 423. If flow is weak or pressure stays low, pull the pump (approximately 30 kg) and check the system relief valve spring free length against the spec of 52.25 mm; test length under 2135 ± 213.5 N load must reach 47.96 mm. Torque the relief valve lock nut to 88 N·m on reinstall.

Remove the transmission per and measure output shaft end play at the rear. Spec is 0.3-0.5 mm (0.012-0.020 in.) per page 138 — anything outside that range means the bearing needs replacement. While you're in there, check oil pump-to-supply flange end play: same 0.30-0.50 mm window on page 152. For clutch pack overlap, minimum is 2.3 mm on 544E or 2.5 mm on 624E/644E (page 110) — below those numbers and the clutch won't hold.

Inspect the pilot control system. On single-lever machines, measure push plate-to-plunger clearance — spec is 0.000-0.254 mm (0.000-0.010 in.) per page 424; a worn plunger will bleed pressure. On two-lever machines, verify spool return passage exposure in neutral: 1.02 ± 0.10 mm per page 463. If the hydraulic oil looks milky or smells burnt after contamination, run the clean-up procedure on using the portable filter caddy before reinstalling any components.

Bleed the hydraulic brake system per pages 292-293, then check accumulator precharge pressure — it must sit at 3447 ± 172 kPa (page 291). If braking is still soft after bleeding, pull a wet disk brake assembly and measure disk flatness: maximum allowable distortion is 1.14 mm (0.045 in.). Check oil groove depth on brake facings — minimum is 0.38 mm (0.015 in.) per page 275. Disk-to-pinion backlash limit is 1.02 N·m; beyond that, replace the disks.

Bleed air from the fuel system following pages 206-208 — this covers 544E, 624E, and 644E models. On 544E and 624E, also verify injection pump lever override clearance: spec is 2-4 mm (0.08-0.16 in.) per page 223. A lever sitting out of that range will prevent clean fueling regardless of how many times you cycle the starter. Check battery condition first using the test procedures on pages 304-305 — a weak battery on a cold morning can mask what is actually a fuel delivery problem.

Start at the steering cylinder — disassemble and inspect seals per pages 253-261, paying attention to seal installation orientation. Verify steering wheel-to-shaft nut torque is 68 N·m (50 lb-ft) per page 240 before assuming internal damage. Check the secondary steering system (pages 238-274) for pressure loss; release residual hydraulic pressure first by cycling all valves as shown on page 68. If the cylinder checks out clean, the issue is likely in the steering hydraulic schematic circuit shown on page 246.