Part of the John Deere Repair Manuals.
Which feed roll procedure belongs to which machine is the sort of question only the factory book settles, and TM1203 answers it across 491 pages covering all four John Deere forage harvesters in the 3940 through 3970 range. The hydraulic section of this John Deere 3950 technical manual PDF opens with system components diagrams for the 3940/3960 and the 3950/3970, then works through the electrohydraulic valve, cutterhead lift system, hydraulic downstop and spout cap cylinder. On the electrical side, harness repair, functional checks and wiring diagrams run from component location through IRON-GARD metal detector, SPOUT-TRAK and ROW-TRAK, while Diagnosing Malfunctions charts front nearly every system section and point you at the test before the teardown. Set shifting fork-to-case clearance to 0.060 in. (1.52 mm) and fill the feed roll gear case with 3 qt (2.8 L). Nobody enjoys pulling the cutterhead twice in chopping season. Bookmarked by section and sharp enough to print, it is bought once and yours for as long as you run this harvester.
What's Inside This John Deere 3940, 3950, 3960, 3970 Manual
| System | Pages | Key Topics |
|---|---|---|
| General Information | 7-30 | Safety, Specifications |
| Drive Train | 31-140 | Diagnosing Malfunctions, PTO Hookup-Recirculating Ball Slip, PTO Hookup-Non-Metallic Bushing Type, PTO Hookup-Grobe Spline Type, Powershaft, Bevel Gear Case, Feed Roll Gear Case |
| Hydraulic System | 141-238 | Diagnosing Malfunctions, Electrohydraulic Valve, Tongue Position Cylinder, Hydraulic Shift Cylinders, Cutterhead Lift System, Hydraulic Downstop, Spout Cap Cylinder |
| Electrical System | 239-322 | Component Location, System Functional Checks and Diagnosing Malfunctions, Tests and Adjustments, Harness Repair, Iron-Gard Metal Detector, Spout-Trak, Downstop and Float Systems |
| Cutterhead Assembly | 323-452 | Diagnosing Malfunctions, Feed Rolls-3940/3960, Feed Rolls-3950/3970, Smooth Roll Scraper-Stationary Knife and Adjuster, Radius and Feed Roll Arms, Knife Sharpener |
| Miscellaneous | 453-482 | Auger, Wheels, Fan and Spout |
| Dealer Fabricated Tools | 483-486 | Cutterhead Stands, Angle, Pipe, Plate |
Quick Reference Specifications
| Specification | Value | Page |
|---|---|---|
| 3940/3960 | ||
| Knife Adjuster Nut (Original Style) | 70 lb-ft (95 N·m) | p. 393 |
| Adjuster Rod Nut-to-Slotted Nut (Original Style) | 85 lb-ft (115 N·m) | p. 393 |
| All Models | ||
| Shifting Fork-to-Case Clearance | 0.060 in. (1.52 mm) | p. 95 |
| Countershaft End Play | 0.070 in. (1.78 mm) | p. 95 |
| Smooth roll shaft TIR tolerance | 0.006 in. (0.152 mm) | p. 369 |
| Smooth roll TIR tolerance at top length | 0.015 in. (0.380 mm) | p. 369 |
| Fan Mounting Nuts Torque | 85 lb-ft (115 N·m) | p. 469 |
| End of Fan Blade-to-Band Clearance | 0.040-0.080 in. (1-2 mm) | p. 469 |
| Side of Fan Blade-to-Sidesheet Clearance | 0.30-0.40 in. (7-10 mm) | p. 469 |
| Bevel Gear Case (One Piece) Input Shaft Rolling Torque | 5-10 lb-in. (0.7-1.4 N·m) | p. 86 |
| 3950/3960/3970 | ||
| Rear Sheave Hub Cap Screw Torque | 85 lb-ft (115 N·m) | p. 469 |
John Deere 3940, 3950, 3960, 3970 Common Problems This Manual Covers
Poor or ragged cut and excessive cob lengths in corn silage
The cutterhead chart on page 326 starts with dull knives: sharpen them. A worn stationary knife gets rotated end for end or replaced, and excessive clearance between the stationary knife and the cutterhead knives is adjusted per Section 50. Then check for a length-of-cut setting that is too long, feed rolls set too far apart (readjust the downstops) and material packed between the feed roll arms and downstops.
Manual Section: Diagnosing Cutterhead, Auger and Fan p. 326Weak fan or spout blow, crop not reaching the wagon
Page 327 lists a hole in the spout liner, excessive blade-to-band clearance, a fan that is not installed properly, the harvester not running at proper PTO speed, and haylage residue on the blower and spout liners. Replace a holed liner, reset the blade clearance to 0.040-0.080 in. (1-2 mm) end of blade to band (fan specifications, page 469), and wash residue off with water.
Manual Section: Diagnosing Cutterhead, Auger and Fan p. 327Feed rolls wrapping or not rising to the top without spinning out
The feeding difficulties chart on page 328 says to install flute fillers when the rolls wrap, and to remove build-up or replace a worn upper rear feed roll. If the rolls will not go to the top without spinning out, remember the maximum usable rise with a full set of knives is 4-3/4 inches (121 mm), then replace or adjust the feed roll springs (Section 50, Group 10 or 11).
Manual Section: Diagnosing Cutterhead, Auger and Fan p. 328PTO hookup vibrates severely or hammers in mild turns
Page 34 traces most of it to hitch geometry. Set the drawbar to ASAE standard for PTO speed and size, center the drawbar on the PTO, and raise or lower the tongue to level the hookup. Use the front set of tongue extension bar holes with 1000 rpm and the rear set with 540 rpm, fit the equal angle hitch the chart specifies, and replace failed bearings at the pedestal.
Manual Section: Diagnosing PTO Driveline p. 34Some electrohydraulic functions work erratically or not at all
Page 155 names loose, broken or disconnected wires at the solenoid or switch, a poor ground at the nut on top of the solenoid, poor battery or wiring connections at the tractor, a failed solenoid coil, terminal contact between adjacent solenoids, and air in the hydraulic system. Swap the suspect coil with a working one before replacing it, rotate solenoids apart, and cycle the harvester functions several times to purge air.
Manual Section: Diagnosing Malfunctions p. 155Frequently Asked Questions
What torque do the John Deere 3940-3970 bevel gear case cover-to-housing cap screws take?
The torque specification for the cover-to-housing cap screws on the bevel gear case (one-piece housing) is 20 lb-ft (27 N·m). p. 73
What is the knife mounting cap screw torque on the John Deere 3940-3970 cutterhead?
The torque specification for the knife mounting cap screws is 110 lb-ft (149 N·m). p. 436
What is the correct feed roll drive chain deflection on a John Deere 3950 or 3970 with IRON-GARD?
For units equipped with IRON-GARD, the feed roll drive chain deflection at mid-span should be 1/8 inch (3 mm). p. 363
What torque do the smooth roll scraper bolts take on the John Deere 3940-3970?
The smooth roll scraper bolts take 85 lb-ft (115 N·m). The same value appears in the feed roll specifications for the 3940/3960 (page 339) and the 3950/3970 (page 363). p. 339
What is the feed roll gear case capacity on a John Deere 3940-3970 forage harvester?
The feed roll gear case has a capacity of 3 quarts (2.8 L). p. 95
Is this John Deere 3940 manual a download or a disc?
You download the Technical Manual yourself: 491 pages, non-searchable PDF, available immediately. Keep a copy on every device you use.
Are there any print restrictions on this John Deere 3940 manual?
Yes, printing is unrestricted: a single page, a chapter, or the lot, on letter or A4.
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