Part of the New Holland Repair Manuals.
This 192-page New Holland HM234, HM235, HM236 Repair Manual (OEM #87392141) puts every process drive, frame, and rotary cutting procedure for your Disc Mower in one place. Inside you'll find a full torque specification section, exploded views of the process drive and pinion assemblies, and step-by-step procedures covering PTO removal, shield service, and cutting head rebuilds. You get the fluid capacity charts too, so you're not mixing up gearbox oil by guesswork. Check pinion shaft backlash against 0.1125-0.3 mm before you button up the housing, and note the oil seal's self-tapping screws seat at roughly 6mm depth. No more flipping through a parts catalog hoping the diagram matches your serial number. Bookmarked by section (Introduction, Power Train, Body and Structure, Tool Positioning, Crop Processing), so you jump straight to the mower deck instead of hunting page by page. Pull it up on your phone at the mower and get the blades turning again.
What's Inside This New Holland HM234, HM235, HM236 Repair Manual
| System | Pages | Key Topics |
|---|---|---|
| Introduction | 5-28 | Legal Advice, International Symbol, Safety Rules Precautionary Statements, Decals, Basic Instructions How to Use and Navigate Through This Manual, Torque Specification Tables |
| Power Production | 29-48 | PTO Power in |
| Power Train | 49-118 | Process Drive Primary Process Drive |
| Body and Structure | 119-136 | Frame Secondary Frame, Shield |
| Tool Positioning | 137-154 | Lifting |
| Crop Processing | 155-192 | Cutting Rotary Disc Cutting |
Quick Reference Specifications
| Specification | Value | Page |
|---|---|---|
| CUTTING Rotary disc cutting | K.10.E | p. 20 |
| PTO POWER IN | B.90.A | p. 22 |
| PTO from disc mower, turn twist collar (1) | counterclockwise to release ball detent | p. 34 |
| self-tapping screws for oil seal | approximately 6mm (.25" inch) | p. 73 |
| Pinion shaft backlash | 0.1125 - 0.3 mm | p. 89 |
| Boom break-away assembly tension | 51.5 mm (2 in) | p. 126 |
| NPT Pipe Fitting Torque (1/2" - 14) | 41 Nm | p. 23 |
| ORFS Connection Torque (Metric, 12mm Tube OD) | 43-47 Nm | p. 25 |
| Split Flange Mounting Bolt Torque (1/2" - 13) | 74-88 Nm | p. 25 |
| 37° Degree Flare Fitting Torque (SAE Dash -6) | 27-33 Nm | p. 26 |
| Cutter Bar Cutting Height | 16 to 60 mm | p. 27 |
| Disc Speed | 3154 RPM | p. 27 |
New Holland HM234, HM235, HM236 Common Problems This Manual Covers
New Holland HM234 drive module pod grinding noise, discs not rotating or rotation is intermittent
Drain the gearbox and inspect for metal in the oil, a sign of worn bearings inside the drive module pod. Check the gearbox troubleshooting chart for noisiness and bearing damage causes. Verify pinion shaft backlash falls within 0.1125 to 0.3 mm; if it's outside spec, the bearings or pinion need replacement before you put this back in the field.
Manual Section: Gearbox Common Problems, Causes, and SolutionsCutter bar vibrates hard or the bar itself cracks after a full season of hay cutting
Stop and check whether the cutter bar oil was changed this season; skipped changes are the number one cause of premature bar and gear wear. Check the fluid level per the procedure on page 180 and refill if low. Inspect discs for bends or cracks and knives for wear or elongation using the checks on page 186; any disc mounting hole elongation over 2 mm (0.08 in) means the disc gets replaced, not reused.
Manual Section: Cutter Bar Disc and Knife Inspection p. 186Disc mower blades work loose or the retaining nut backs off during cutting
Torque the blade nut to 160 Nm (118 ft-lb) per the spec on page 189, and re-torque every 15 hours since these nuts settle in fast on a new blade set. Replace the nut and mounting bolt every 5th knife change regardless of how they look, per the interval on page 187. Don't reuse a nut that's already been backed off once; it won't hold torque reliably a second time.
Manual Section: Cutter Bar Knife Replacement p. 189PTO shaft clunks or binds when engaging, U-joint feels loose
Pull the front and rear PTO shields (each turns 180 degrees counterclockwise to release, per page 35) and inspect the U-joint cross and bearing cups for wear or pitting. When you drive the top bearing cup out, expect the yoke ear to move about 8 mm (0.25 in) before it clears; if it won't budge, the cup is corroded in place and the joint needs a full teardown per the overhaul procedure starting on page 36.
Manual Section: PTO Shaft U-Joint Overhaul, Inspection, and Repair p. 36Gearbox cover leaks oil or won't seal after reassembly
Check the self-tapping screws holding the oil seal; they should sit approximately 6 mm (0.25 in) proud per the spec on page 73, and a seal that isn't seated to that depth will weep. Torque the cover bolts to 5-6 Kgm (36-47 lb ft) as specified on page 92; overtightening warps the cover and is a common cause of repeat leaks on these gearboxes.
Manual Section: Gearbox Fluid Level Check and Adjustment p. 92Boom breakaway assembly won't release cleanly after hitting an obstruction in the field
Remember this HM series has no break-away hubs, so the boom breakaway is your main protection against impact damage; don't skip this check. Inspect the assembly for free sliding, bent studs, and ball joint end play per the procedure on page 124. Confirm tension travel measures 51.5 mm (2 in) as specified on page 126; if the rubber tensioner is compressed short of that, replace it before the next field pass.
Manual Section: Boom Breakaway Component Inspection p. 126Frequently Asked Questions
What are the torque specs for disc bolts on HM235 and HM236?
For the knife nut, the torque specification is 160 Nm (118 Foot pounds). It is crucial to re-torque all removed knife fastening hardware to this value after the first use and then check regularly every 15 hours. For the self-locking nut that secures the disc to the cutter bar, the torque is 320 Nm (236 Foot pounds). p. 189
What is the approximate oil capacity for the gearbox on the New Holland HM234, HM235, and HM236 disc mowers?
The gearbox oil quantity is approximately 700 mL (23.5 US fl oz). It is important not to overfill the gearbox with lube oil to ensure proper operation and longevity. p. 64
What are the oil quantities for the cutter bar on the New Holland HM234, HM235, and HM236 disc mowers?
The cutter bar oil quantities are approximately 1600 mL (54 US fl oz) for the 4 Disc Mower (HM234), 2300 mL (78 US fl oz) for the 5 Disc Mower (HM235), and 2900 mL (98 US fl oz) for the 6 Disc Mower (HM236). p. 157
What type of gear oil should be used for the gearbox and what is the recommended oil change interval for the New Holland HM234, HM235, and HM236 disc mowers?
Only brand approved API GL-5 80W90 gear oil should be used for the gearbox. The initial oil change is recommended after the first 50-80 hours of operation, with subsequent changes occurring after 700-750 hours of operation or at least once per 12-month operating period, whichever comes sooner. p. 94
How do I adjust the drive belt tension on the New Holland HM234, HM235, and HM236 disc mowers?
To adjust the drive belt tension, turn the tension nut clockwise to increase tension or counterclockwise to decrease it. Proper belt tension is achieved when the center point of the belts, located between the two pulleys, deflects approximately 20 mm (3/4 in) when pressure is applied. p. 112
How quickly can I access this New Holland HM234, HM235, HM236 manual after?
Immediate download of the complete 192-page searchable Repair Manual. Access it on any device, from a laptop at your desk to a phone in the field.
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