Part of the New Holland Repair Manuals.
That gearbox is the deepest job in this 12-page New Holland 438 service manual PDF, and the teardown takes your disc mower's drive from cover removal through the pinion gear, Woodruff key, and bevel gear to reassembly with the adjustment nuts set right. The cutter bar takes up the rest of the book: removing it from the base frame, splitting the halves open, servicing the disc gear bearings and hubs, then bolting it back on with the drive belts and sheaves lined up. Exploded views back up the procedures, so spacers and roll pins go back in the right order. Press the idler gear bearing snap ring free at 20 tons, and torque the cutter bar pivot support bolts to 120 ft. lbs. on reinstall. Every dry afternoon this mower sits in pieces is hay left standing. Bookmarked and text-searchable, the PDF goes to whatever barn or shed the 438 sits in, keeping your specs with the machine.
What's Inside This New Holland 438 Manual
| System | Pages | Key Topics |
|---|---|---|
| Removing the Cutter Bar From the Base Frame | 2 | Cover and Guard Assembly, Swath Board Assembly, Belt Shield, Drive Belts, Pivot Support, Hinge Pin |
| Opening the Cutter Bar | 3-4 | Crop Divider End Cap, Discs, Outer Skid Shoe, Cutter Bar Halves, Inner Shoes, Disc Shoes |
| Disc Gear Bearings and Hub | 5-6 | Disc Gear Shaft, Bearings, Roll Pin, Disc Hub, Spacer, Housing |
| Cutter Bar Assembly | 7 | Upper Trough, Idler Gears, Tapered Washers, Allen Head Stud Bolts, Skid Shoes, Disc Hubs |
| Gear Box Disassembly and Assembly | 8-9 | Gear Box Cover, Output Shaft, Pinion Gear, Woodruff Key, Bevel Gear, Input Shaft |
| Attaching the Cutter Bar to the Base Frame | 10-12 | Cutter Bar, Bolts, Drive Belts, Sheaves, Pivot Points |
Quick Reference Specifications
| Specification | Value | Page |
|---|---|---|
| Allen head stud bolts torque | 60 ft. lbs. | p. 8 |
| Adjustment nuts on shafts torque | 50 ft. lbs. | p. 9 |
| Idler gear bearing snap ring removal pressure | 20 tons | p. 6 |
| Gear box bearing pre-load | 12 in. lbs. | p. 9 |
| Bearing support nut torque | 60 ft. lbs. | p. 9 |
| Cutter bar attachment bolt torque | 120 ft. lbs. | p. 10 |
| Drive belt deflection force | 25 lbs. | p. 10 |
New Holland 438 Common Problems This Manual Covers
New Holland 438 cutterbar grinding and binding, discs jerk and stall in heavy hay
Shut the PTO off and open the bar before wear takes out every gear in line. Remove the discs, outer skid shoe, and split the cutter bar halves following page 3. Inspect each gear for chipped teeth and check bearings for roughness. Retime the gears on reassembly and torque the Allen head stud bolts to 60 ft. lbs.
Manual Section: Opening the Cutter Bar p. 3Idler gear teeth stripped or bearing seized, one or two discs quit turning
Split the cutter bar and lift the upper trough to reach the idler gears, following the layout on page 7. Replace any gear with chipped or polished teeth along with its bearing. Bring the bar to a shop with a press; the idler gear bearing snap ring can need 20 tons of pressure to remove.
Manual Section: Cutter Bar Assembly p. 7Disc wobbles with vertical play in the hub, rumble from the cutterbar at PTO speed
Grab each disc and check for vertical play with the PTO shut off. Pull the disc hub, spacer, and roll pin, then press the disc gear shaft and bearings out of the housing per page 5. Fit new bearings in pairs, and torque the Allen head stud bolts to 60 ft. lbs. when you close the bar.
Manual Section: Disc Gear Bearings and Hub p. 5Gear box whines under load and weeps oil around the input shaft
Drain the gear box and check the oil for glitter before condemning it. Tear it down per the procedure starting on page 8, replacing the input shaft seal and any pitted bearing. Seat the bearings by torquing the adjustment nuts to 50 ft. lbs., then back them off to a 12 in. lbs. pre-load.
Manual Section: Gear Box Disassembly and Assembly p. 8Drive belts squeal in thick crop and the cutterbar slows or stops
Check belt tension before blaming the gear box. Tighten the drive belts until it takes 25 lbs. of force to deflect them 1/2 in. midway between the sheaves, following page 10. Replace glazed or cracked belts as a set, and while the shields are off, verify the cutter bar pivot bolts are torqued to 120 ft. lbs.
Manual Section: Attaching the Cutter Bar to the Base Frame p. 10Frequently Asked Questions
What are the torque specifications for the cutter bar bolts on a New Holland 438 disc mower?
When reassembling the cutter bar, apply R.C. 35 Loctite to the seven allen head stud bolts and tighten them to 60 ft. lbs. of torque. p. 8
What is the procedure for adjusting the drive belt tension?
Tighten the drive belts until it requires a force of 25 lbs. to deflect the belts 1/2 inch at the midpoint between the sheaves. p. 10
What pressure is required to shear the snap ring during idler gear bearing removal on a New Holland 438?
To remove the idler gear bearing, support the bottom of the gear hub with a heavy spacer and press against the special tool until the snap ring shears, which requires approximately 20 tons of pressure. p. 6
What are the torque specifications for the gear box adjustment nuts on a New Holland 438 disc mower?
Tighten the adjustment nuts on the shafts to 50 ft. lbs. torque to properly seat the bearings, then back them off to achieve a 12 in. lbs. pre-load. p. 9
Is this manual a PDF I download?
All 12 pages arrive as one searchable PDF at checkout. Read it at the desk, then take the phone out to the machine.
Can I print just the pages I need from this manual?
Yes, print as many copies as you want, and there are no restrictions. Many mechanics print the section they need and bring it to the shop floor.
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