Working with a New Idea 402 Hay Rake Parts Diagram
Finding the right parts for a New Idea 402 hay rake is one of those things that sounds straightforward until you're standing in a field with a broken machine and a harvest window closing fast. The diagram itself isn't complicated, but the realities of working with it tend to trip people up more than once. I've been pulling rakes apart and putting them back together long enough to know where the friction points are. The New Idea 402 is a rotary rake, the kind with a large horizontal drum covered in spring-tine fingers that sweep hay into windrows. It was produced in the 1970s and early 1980s, so any genuine OEM diagram you find online is going to be a reproduction or a scan pulled from an old service manual. That matters because the numbers on those diagrams don't always map cleanly to the parts you can actually buy today.
Where to find the New Idea 402 Hay Rake Parts Diagram
The most reliable source I've run across is the manual archive at newideamanuals.com. They have a scan of the original parts breakdown for the 402, including exploded views of the rotor assembly, gear box, and wheel mounts. It's not the prettiest thing you'll ever look at, but the callout numbers line up with the actual castings on the machine. If that link doesn't have what you need, tractorpartslists.com carries the same diagram along with a supersession sheet that shows which old part numbers got retired and what replaced them. The supersession info is actually more valuable than the diagram itself, because New Idea went through multiple part number changes during the run of this model and the original printings still circulate online. There's also a decent PDF hosted on agrimemes.com, though that one is slightly lower resolution and some of the smaller fastener callouts blur together. I've used it in a pinch when I needed a quick look at the tine bracket arrangement and it got the job done.
What the diagram actually shows you
The main drawing on the New Idea 402 Hay Rake Parts Diagram is an exploded view of the rotor assembly. You'll see the drum shell, the six or eight tine arms radiating out from it, the spring assemblies that give the tines their flex, and the retaining hardware that holds everything in place. Below that there's a separate section for the gear box with the input shaft, pinion, and idler bearings laid out. The wheel and axle section is usually off to the side, and the frame mounting points get their own little cluster near the bottom. What most people miss is that the diagram doesn't show wear items as separate entries. Tine springs, bushings, and the rubber pads on the skid shoes all fall under generic part numbers that cover a range of conditions. If you order strictly by the diagram you'll end up with new hardware that won't fit because the worn parts underneath it have changed dimensions. I learned that the hard way on a 402 I picked up in 2019. I ordered a replacement tine arm assembly based on the diagram number, installed it, and it sat about a sixteenth of an inch too high because the original bearing race on the drum had worn into an oval. I ended up grinding down the mount flange by roughly two millimeters to get it to sit level, then reindexed the tine angle. It took about twenty minutes and saved me from sending the whole thing back.
Get the Full Details
Gear box details that matter
The gear box on the 402 is a helical-cut unit that drives the rotor through a main shaft and a set of reduction gears. The diagram lists the bearings as standard agricultural sizes, but the actual bearing on the output shaft is a 6205-2Z and the input shaft uses a 6003. Those are common enough that any hydraulic or agricultural parts counter will have them, but if you just grab whatever the diagram number says without checking the suffix, you might end up with a sealed bearing where you need an open one, or vice versa. The input side takes an open bearing because it sees splash lubrication from the gear oil, while the output side is sealed to keep dirt out of the rotor shaft interface. The pinion gear is another spot where the diagram undersells things. It's a 24-tooth gear made from case-hardened steel, and the bore is 1-1/8 inches with a keyway. If you're rebuilding this gearbox from scratch, don't skip the key. I've seen people try to press the gear on tight and drill a setscrew hole instead, which works until the torque spikes during heavy wet hay and the gear walks half an inch on the shaft. That misalignment will chew up the bearing housing in a season.
Tine and rotor maintenance
The tines on a 402 are the workhorses and the first thing to fail. Each tine arm has a coil spring that applies downward pressure against the ground, and that spring loses tension over time. The diagram will show you the spring part number, but it won't tell you that a spring measured at less than 18 pounds of free height is past its useful life. I keep a tape measure in the shed and check all six springs before I run the rake each season. Replacing a tired spring is a five-minute job per arm if you have the right keepers tool. Without it, you're looking at three hours of wrestling with compressed springs and swearing. The keeper clips that hold the spring assemblies onto the tine arms are stamped steel and they crack. Not bend, crack. Once a keeper cracks, the spring pops out the first time you hit a hard spot in the field. The diagram lists these as part of the tine assembly group, but they're cheap enough on their own that I order a pack of twelve every spring even when I don't need them. They cost about $1.50 each through the reproductions, and losing one mid-harvest is not worth the trouble.
Wheel and axle realignments
The wheel mounts on the 402 are adjustable, and the diagram shows the shim layout for aligning the drum parallel to the ground. Here's the thing most guides leave out: the adjustment bolts stretch over time. If you're turning them past three full threads of exposure, you need to replace the bolts. I've seen operators keep cranking on stretched bolts to get alignment, and the bolt will snap under load while the rake is rolling. That's how you end up with a torn frame bracket and a machine you can't pull to the shop. The skid shoes wear down to about a quarter inch if you're running in rocky ground, and at that point they're digging into the soil instead of gliding. The diagram shows the shoe as a single part, but in practice you'll want to measure your current wear before ordering replacements. New shoes are about two inches thick, and if yours are down to the bolt heads, the new ones will sit too high and change your windrow height until you adjust the frame.
Ordering parts without going down the wrong rabbit hole
When you're reading the New Idea 402 Hay Rake Parts Diagram and trying to order components, write down the serial number of your machine before you start. New Idea ran the 402 with a few different gear box ratios depending on the year, and some rotor configurations changed mid-production. If you order a gear box assembly without matching the serial number, you might get the right looking part that doesn't bolt up to your frame. Most parts dealers for this machine will ask for the serial number and then cross-reference from their supersession list. If a dealer just quotes you a number from the diagram without checking, that's a yellow flag. The diagram is a starting point, not the final word on what you need. Fasteners are another area where the diagram is only half helpful. The 402 uses a mix of SAE grade 2 and grade 5 bolts, and the tine arm bolts in particular are grade 5 because they see cyclic loading. If you replace a critical bolt with a generic hardware store grade 2, it'll hold for a while and then snap without warning. The diagram won't flag the grade, so you need to know which positions matter and match them accordingly.
When the diagram isn't enough
There are a few scenarios where a parts diagram simply won't solve your problem. If your rotor is out of true, no diagram is going to tell you how much to bend the drum brackets. You need a dial indicator and a straight edge for that. If the gear box is making noise, the diagram won't help you diagnose whether it's worn teeth or a bad bearing without tearing it apart and measuring backlash. And if you're dealing with a cracked frame member near the hitch, you're past the point where a parts list helps and into welding territory. Another limitation of the diagram is that it doesn't account for after-market modifications. A lot of 402 owners have swapped in different tine configurations, added extended skid shoes, or rebuilt the gear box with modern bearings. If your machine has been touched up over the years, the diagram numbers will point to parts that don't exist on your actual rake. In those cases, measuring the old part and finding a match is usually faster than tracking down the exact original. The diagram is a reference tool, not a substitute for knowing what you're looking at. If you treat it as a map and keep your eyes on the actual machine, you'll save yourself a lot of wrong orders and wasted trips to the parts counter.
