Automatic Transmission

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Revision as of 04:47, 17 July 2007

Datsun 1200s came with a traditional 3-speed fully automatic transmission. This was the JATCO 3N71B, as used in most Japanese cars in the 1970s. It is a very reliable transmission, typically not needing any service for 10 years or 100,000 miles. The car body is different in the tunnel area: Automatic-equipped cars had a significantly larger front tunnel area. The rear of the tunnel is the same. Cars with automatic weighed 75 pounds more than standard cars. All automatic 1200s have a small shift Console box.

Identification by ID plate: B110...A... means an originally Automatic equipped car. Only sedans and coupes were fitted with autos. Wagons and Trucks (B120) never got them.

A side effect of this larger tunnel means an auto-equipped 1200 is the perfect donor for engine transplants. Larger transmissions fit more easily e.g. 63a B210 5-speed, L-series engine transmissions or CA18, SR20 transmissions.

See: Manual transmission conversion

JATCO stands for Japanese Automatic Transmission Company. JATCO was a joint venture between Nissan and Mazda, both owning 50%. The JATCO unit is very similar to a Ford C4 and almost bulletproof, the only thing that seems to go wrong with them is that (rarely) vacuum modulator diaphram ruptures and ATF gets sucked into the intake manifold, causing them to not shift right and the engine to billow clouds of oil smoke.

Apparently there never was a 4-speed auto available for the A series. 4 speed autos didn't show up until the mid 1980's, by then Nissan had stopped using the A series in any great numbers to make it profitable to do the design and engineering.

The 3-speed automatic is less efficient than the 4-speed manual for two main reasons:

• Some loss of power due to the fluid coupling (Torque convertor). This means top speed is a few mph less. Newer transmissions starting in the 80s overcome with with "lockup" gears
• One less gear. 1st gear in the auto is fine, but there is a big RPM drop going into second. Just as with the manual 3-speed Transmission

Gas Station Information

The rotating torque converter drives the front pump in the trans & circulates oil through the trans & converter. Keep checking the oil level while idling & top up as per the book.

Lubricant: DEXRON ATF (automatic transmission fluid).

IMPORTANT: Check HOT. Not cold. This fluid expands a lot with heat.

Usage

1972 USA Owners manual (see pages 16-17): [Use "D"] for most city and highway driving.

Badges

Auto-equipped 1200s came with 'Nissan Full Automatic' and 'Sports' badges:

See: Badges

Performance

You can use the same methods as with any automatic transmissions:

• A specialty transmission shop can modify the converter to a higher stall, for faster acceleration. NOTE: if it's a khanacross/motorkhana car, you won't want ANY STALL at all. The stall means it won't move until the engine revs up, which is good for drag racing.
• If you want to favor low-speed operation, fit 4.10 gears from the 1200 wagon or ute to your coupe or sedan
• No lockup converters are available. This generally takes a different transmission design. It would only help high-speed running anyways, it wouldn't help to make the car accelerate faster

Discussion: Race cam 1 with an automatic?

Conversion

Automatic-equipped cars had a significantly larger front tunnel area. The rear of the tunnel is the same. For this reason you can easily convert an Auto car to a Manual car. Do go to automatic you may need to modify the tunnel.

For details, see Manual transmission conversion