Description

Datsun 1200 1973 Service Manual

You know the drill. A transmission comes in, customer wants it done by Friday, and the aftermarket manual you obtained gives you a torque spec for some other year. That’s wasted hours. This 1973 Datsun 1200 Service Manual is the factory document. 513 pages of what Nissan actually stamped into the steel. No reprints, no third-party guesses. If you’re touching a 3N71B automatic transmission in a B110 series, you need this on the bench.

Section AT starts with the hydraulic control system on page AT 4. The manual spells out fluid requirements: DEXRON only. The torque converter is welded shut, so you will not disassemble it. Period. The identification number is stamped on the right side of the case, and the manual shows you exactly where. I have seen techs skip that and order wrong parts. Don’t be that guy.

Hydraulic Control System: What’s Actually Inside

The 3N71B uses two planetary gear sets, two multiple-disc clutches, a band brake, and a one-way sprag clutch. The factory manual breaks down each valve body passage. The trouble diagnoses section starting on page AT 49 gives you pressure checks and shift point tests. Need the charge pressure spec? Page 73. Not page 72, not a generic book. That page.

Gear ratios are listed for all three forward speeds and reverse. The selector positions P, R, N, D, 2, and 1 each have a specific hydraulic circuit. The manual shows the flow paths. You want to know why 2 range locks out third gear? It’s in the description. No guesswork.

3 Common Automatic Transmission Problems the Manual Addresses

First: no drive in forward but reverse works. The manual walks you through the hydraulic pressure test at the clutch apply ports. Second: slipping on 2-3 shift. That’s often the band servo or the accumulator. Page 49 outlines the adjustment procedure. Third: harsh engagement from Park to Reverse. The service data on page AT 60 includes the correct line pressure at idle. Compare your gauge reading to that table.

Each problem has a specific diagnostic path. No flowcharts that lead nowhere. Real factory bulletins from 1973.

Removal and Installation Sequence

Section AT 33 covers removal. You need a transmission jack, a set of metric sockets, and a torque wrench that reads in ft-lbs. The manual lists the bellhousing bolt torque. The torque converter to drive plate bolts: spec is 33 to 41 ft-lbs. Use a cross pattern. I have seen stripped threads from people zipping them with an impact. Do not. The manual also shows the converter drain plug orientation. Install it wrong and you get a vibration that sounds like a loose heat shield.

Installation is reverse, but the manual includes a step to check converter engagement depth. Measure from the bellhousing face to the converter hub. Must be at least 2.5 mm clearance. Miss that and the pump will get chewed up on first startup.

Does the Manual Cover the Torque Converter?

Yes, but not in the way you might expect. The converter is a welded unit – no service apart from replacement. The manual tells you the correct stall speed range and the identification marks. It also specifies the fluid capacity after converter drain: about 5.5 quarts. Use DEXRON only. Some aftermarket sources suggest Type F. That is wrong. The factory manual is clear.

Why OEM Factory Specs Beat Aftermarket Copies

Aftermarket manuals often combine years or leave out torque values. This one is specific to the 1973 Datsun 1200. The service data table on page AT 60 includes line pressures, shift speeds, and clutch clearance specs. You cannot get that from a generic book. The manual also references the chassis section for driveshaft and rear end specs. If you need the whole vehicle, check the related Datsun 1000 1200 Workshop Manual or the Datsun 1200, 510, 610, B210, 710 Service Manual – 245 Pages for broader coverage. For later years up to 1978, the Datsun 1200, 510, 610, 710, 810 Repair Manual 1973-1978 fills that gap.

Industry standards like those discussed in the Automotive Industry Overview show why factory documents are the benchmark. The Automotive Industry Overview confirms that OEM specs prevent comebacks.

FAQ

Does this manual include wiring diagrams?

No. This is the transmission and chassis section only. The electrical schematics are in the full service manual set.

How do I verify the transmission identification number on my 1973 Datsun 1200?

The manual says the plate is on the right side of the transmission case. Look for a stamped number starting with “3N71B”. The example on page AT 2 shows the format. Use that code when ordering parts. If the plate is missing, measure the bellhousing bolt pattern and compare to the drawing in the manual. Some later units had a different bolt circle. The manual also lists the serial number arrangement so you can decode the production month.

You have a job ahead. Do not rely on a photocopy of a photocopy. Access the Factory Manual and get the torque specs from the source that built the car.