Is there any difference in the automatic transmissions of a 1990 Chevy truck that came with 4.3 or 350 engine?

The 1990 Chevy truck with a 4.3L engine came with a 700R4 automatic transmission, while the truck with a 5.7L engine came with a TH350 or TH400 automatic transmission. The two transmissions are similar, but there are some key differences between them.

* The 700R4 is a four-speed transmission, while the TH350 and TH400 are three-speed transmissions. This means that the 700R4 has an additional gear that allows it to shift into a lower gear when needed, which can improve fuel economy and performance.

* The 700R4 has a lock-up torque converter, while the TH350 and TH400 do not. A lock-up torque converter locks up the transmission's torque converter at higher speeds, which reduces slipping and improves fuel economy.

* The 700R4 has a computer-controlled shift pattern, while the TH350 and TH400 have mechanically controlled shift patterns. The computer-controlled shift pattern allows the 700R4 to shift gears more smoothly and at the optimal time, which can improve fuel economy and performance.

Overall, the 700R4 is a more advanced transmission than the TH350 and TH400. It has more gears, a lock-up torque converter, and a computer-controlled shift pattern. These features can improve fuel economy, performance, and shift quality.