* Case Size and Mounting: Truck and van chassis are different, meaning the transmission cases are different sizes and have different mounting points. The bellhousing (which bolts to the engine) will also be different.
* Transfer Case: The truck transmission is designed to mate with a transfer case for 4-wheel drive, which a van transmission doesn't have.
* Gear Ratios: Even if the physical dimensions *somehow* matched (they won't), the internal gear ratios are likely optimized for different applications. A truck needs low gears for off-roading and hauling, while a van prioritizes fuel economy and towing capacity at lower speeds.
* Output Shaft: The output shaft (which drives the driveshaft) will have different lengths and potentially different spline counts.
In short, while both vehicles might use automatic transmissions, they are designed for entirely different purposes and are not interchangeable. Attempting to do so would require extensive and likely impossible modifications.
