Thks 57 Pathfinder, correct on the 1982.

- of the square body GMC trucks I've owned

- my 1984 Sierra had a 3 speed transmission & '85 had the 4 speed (if I recall).

In the Beginning
The 700-R4 was first introduced in the 82 Corvette. On paper, its specs looked pretty good: The trans had lower First and Second gears (3.06 and 1.63, respectively) than other automatics, its lockup torque converter offered potential fuel-mileage gains, and the 0.7 overdrive decreased the overall drive ratio by 30 percent. But the original design was not considered a strong transmission, with failures behind even a mild 350 not uncommon. The trans was so weak that in its original setup, GM deliberately calibrated it to kick out of lockup and high gear under full-throttle, top-end conditions to avoid burning it up. The original versions had only downsized, 27-spline input shafts, one of many possible and common failure points. By 1984, 700-R4s intended for use behind small-block Chevy V-8s began to receive beefy, 30-spline input shafts similar to those found on classic TH350 and TH400 transmissions. From 1984 to 1987, the most failure-prone internal parts, from the ring-gear to the oil-pump housing, were upgraded. An auxiliary valvebody was added in October 1986. Finally, on performance cars like the Corvette, additional internal lubrication improvements permitted the trans to survive in high-gear, full-throttle, top-end conditions. Many of the improvements can be retrofitted into the earlier, weak transmissions, but the 27-spline versions need so many new parts that its more cost-effective to swap in a later core. However, it is worthwhile to upgrade the later 30-spline versions to Corvette/IROC-level internals, if theyre not already so equipped.