Working on a Fiat 680? Here's What You Actually Need
The Fiat 680 is a mid-range tractor from the late 1960s to early 1970s, and finding a clean workshop manual for it has become genuinely frustrating over the years. Most of what's floating around online is either a blurry scan, a poorly OCR'd PDF, or a listing that charges you twelve bucks for something you can get for free. The manual itself covers the 680 NM variant primarily, with the same engine family used across several Fiat models of that era. I spent about three days tracking down a proper version last year when a hydraulic lift arm on my 680 refused to hold position. The issue wasn't in the lift pump or the relays—it was the hydraulic control valve spool wearing a groove in its bore. The factory manual had the exact teardown procedure and wear limits for that valve. Without it, I would've just kept swapping parts until the thing ran right or I gave up.
Fiat 680 Tractor Workshop Manual
The workshop manual is organized by system: engine, transmission, hydraulics, electrical, and final drive. It includes torque specs, clearance tolerances, and step-by-step disassembly sequences. The engine section alone covers the Fiat 1157 inline-four diesel—6.8 liters, 80 horsepower at 1800 RPM. That engine was carried over from earlier models, so parts and knowledge are more available than you'd think, but the hydraulic and transmission details are specific to the 680. One thing most people miss: the hydraulic system uses an open-center loader-type circuit, not a closed-center load-sensing design. If you're troubleshooting pressure issues and the manual says "check relief valve," don't just adjust it and call it done. The open-center flow means the pump delivers full flow at low pressure until a circuit is loaded. A lot of beginners adjust the relief valve thinking they've fixed a weak lift, when the real problem is worn piston seals in the lift cylinder or a leaking compensator spool in the control valve. I saw this repeatedly with these machines. Another counter-intuitive point: the transmission uses a constant-mesh four-speed with a creeping gear, and the synchronizers are on second, third, and fourth. First and reverse are sliding collar. If you're grinding into first, it's almost never the synchro—it's the sliding collar teeth wearing rounded. Rebuilding the synchros won't fix a first-gear grind. The manual shows the exact wear limits for the collar teeth, which most aftermarket guides skip entirely.
Here's where it gets tedious. The electrical section uses Fiat's older 12-volt negative-ground system with a mechanical voltage regulator and a 35-amp generator. These days you'll find people swapping in alternators, and that works fine, but the wiring diagram in the manual uses Italian color codes. Brown, red, yellow, green, blue. If you're tracing a fault and your multimeter beeps through what you think is the starting circuit but it's actually the pre-heating circuit, you're going to waste an afternoon. The manual's wiring diagrams are clear, but they're printed in black and white, so color identification relies on the legend. Print the legend on a separate sheet and keep it next to the tractor. As for getting the manual: it's out of print and Fiat hasn't reissued it. The best source I've found is the Italian agricultural machinery archives, where collectors have scanned the original Fiat Avanzatori editions. There's a German collector site that hosts a complete set—engine, transmission, hydraulics, and electrical—roughly 180 pages, scanned at decent resolution. Another option is the Fiat 680 owners forum, where someone uploaded a PDF that's readable but has a few pages missing in the final drive section. If you need the final drive specs, which you will if you're dealing with axle seal leaks, get the full set from the archive version. There are also reproduction print-on-demand copies sold on a few marketplaces. They run about thirty to forty dollars and the binding is serviceable, but the print quality is noticeably duller than the scanned PDFs. If you're working on a tractor in a dusty shed, a physical copy has obvious advantages. If you're doing research before you pull anything apart, the PDF is faster to search.
Get the Full Details
One practical note about the manual's torque specs: Fiat listed them in meter-kilograms for the European edition. The English translations you find online sometimes leave the units as MKG when they should say kgf·m. They're the same thing numerically, but if you're using a torque wrench calibrated in newton-meters or foot-pounds, you need to convert. A quick conversion: 1 kgf·m equals about 9.8 newton-meters, or roughly 7.2 foot-pounds. The engine head bolts, for example, are 5.5 kgf·m, which works out to about 54 newton-meters or 40 foot-pounds. Tighten those by feel and you'll warp the head gasket within a season. The manual also doesn't cover every factory modification that happened during the 680's production run. Early models from 1968 had a different oil pump housing than the 1972 and later versions. If you're sourcing parts from a salvage yard and the swap isn't bolt-on, check the casting numbers against the manual's parts lists. The manual itself notes the change in a footnote, but it's easy to overlook. If you're doing a full restoration and the manual isn't giving you everything, the Fiat 680 owners group in Italy maintains a parts cross-reference that maps OEM numbers to third-party suppliers. Most of the wear items—seals, gaskets, bearing sets—are available through agricultural parts distributors in Europe, but in the US you're often looking at specialty suppliers or cannibalizing another unit. The manual's part numbers will help you identify exactly what you need rather than guessing based on the tractor's serial number, which Fiat didn't always correlate to configuration changes in a straightforward way.
The bottom line is that the workshop manual is still the single best reference for this tractor, even though it's nearly sixty years old. The information is accurate for the machines as they left the plant. Gaps appear mostly around field modifications and wear limits that Fiat never bothered to document because they expected components to be replaced rather than rebuilt. For the things the manual does cover—hydraulic valve servicing, transmission rebuilds, engine timing—the specs are solid and detailed enough that you shouldn't need a second source for most jobs. Just make sure you're looking at the right version and not a truncated excerpt someone uploaded without the hydraulic schematics.
