Nissan 620 1978 Service Manual – 507 Pages of Factory Repair Specs

Description

You ever crack open an aftermarket manual and find torque values that don’t match the hardware you’re holding? Yeah, I’ve seen it. That’s why when I need to work on a 1978 Datsun 620 pick-up, I go straight to the source. This Nissan 620 1978 Service Manual is the same book the dealer techs used. 507 pages of factory procedures, straight from Nissan Motor Co. No guesswork involved.

7 Major Systems Indexed in the TOC

Flip to the Quick Reference Index and you’ll see exactly where each system lives. Engine Tune Up (ET), Engine Mechanical (EM), Cooling System (CO), Engine Fuel (EF), Electrical (EE), Manual Transmission (MT), Automatic Transmission (AT), Propeller Shaft & Differential (PD), Front Suspension (FA), Rear Suspension (RA), and Brake System (BR). Every section has its own table of contents—no hunting through 500 pages when you need a compression spec or bleed procedure.

For a home garage guy, that indexing saves your Saturday. You don’t waste time flipping past body trim sections looking for the clutch slave cylinder. The manual is laid out so a beginner can find the right page without calling a friend who “knows Datsuns.”

Factory Torque Specs vs. Aftermarket Guesswork

I’ve seen aftermarket manuals list head bolt torque for an L20B at 60 ft-lbs when the real value is 58-62 in a specific sequence. That 2 ft-lb difference might not seem like much until you blow a head gasket at highway speed. Nissan printed this manual for their own techs—the torque values, clearances, and fluid capacities are verified. Section GI lists approximate refill capacities and recommended lubricants, including SAE viscosity ratings. You won’t find “use any 10W-30” here; it’s specific.

Does This Manual Cover the Fuel System?

Yes. Section EF covers the entire engine fuel system, from the mechanical fuel pump to the carburetor adjustments. If you’re dealing with a stumble off-idle or a rich idle on a ’78 620, the manual walks through float level, idle mixture, and throttle linkage. It also includes the emission control system (EC) for the stock EGR and air injection. California models have a few extra check valves—the manual shows them.

3 Reasons to Stick with OEM Documentation

First, wiring diagrams. Aftermarket diagrams often combine multiple years and leave out connector pin locations. The Electrical section (EE) in this manual uses factory pin numbers and wire colors. Second, special tools are listed at the end of each section—Nissan wanted their techs using the right puller or compressor, not a hammer. Third, safety. The foreword includes a warning about personal injury and property damage—that’s not a suggestion. A factory manual treats safety like a liability lawyer, which is exactly what you need when you’re under a truck on jack stands.

Transmission Rebuild: What the Manual Says

The manual devotes separate sections to Manual (MT) and Automatic (AT) transmissions. For the manual, you get syncro ring clearance specs, shift fork wear limits, and bearing preload. The automatic section covers the Jatco 3N71B—valve body checks, clutch pack clearances, and the correct ATF type (Dexron II, not the generic “universal” fluid). If you’re rebuilding either, you need these numbers.

Brake System and Suspension: Factory Procedures

Section BR covers the entire brake system: master cylinder, wheel cylinders, disc/drum specs. Rear drum shoe clearance is a common gotcha—the manual gives the adjustment procedure with a feeler gauge. Front and rear suspension (FA, RA) include ball joint wear limits, wheel alignment specs, and torsion bar adjustment for the front. This is a truck that can sag after 40 years—the factory procedure gets the ride height back where it belongs.

Who Needs This Manual?

If you own a 1978 Datsun 620 and want to keep it on the road without paying a vintage shop $150/hour, you need this. The manual assumes you have basic tools (wrenches, sockets, a torque wrench) but does not assume you know every trick. It warns you when a step can damage a part or hurt you. Beginners will benefit from the step-by-step removal and installation procedures—the foreword says it’s for “maintenance adjustments, minor service operations, removal and installation.” That covers a tune-up or a full engine swap.

For the experienced mechanic, the manual is still worth having because it’s the definitive reference. You don’t memorize every spec on a 45-year-old truck. Keep this on the bench, not in a file cabinet.

Does this manual have wiring diagrams for the entire truck?

Yes. Section EE covers the complete body electrical system, including the instrument panel, lighting, and ignition. You get the factory schematic with color codes and connector views. Aftermarket diagrams often skip the turn signal circuit—this one includes it.

What about the air conditioning system?

Section AC covers the factory A/C components. If your truck has dealer-installed A/C, this may not match exactly, but the compressor and evaporator specs are here.

If you’re tired of chasing down specs that don’t exist, get the real thing. Access the Factory Manual now.