TCI Maximizer 4×4 Transmissions 371402

At 550 advertised horsepower, this remanufactured four-speed automatic rates higher than the transfer-case-specific Maximizer units elsewhere in this range, and it's purpose-built for heavy-duty four-wheel-drive use with lockup compatibility, a forward shift pattern, and the Chevy bellhousing fit.

What the horsepower rating tells you

That 550 rating points to a build meant for trucks pushing more power through the drivetrain than a stock engine, while still being set up for the demands of four-wheel-drive service rather than pavement-only use. The input shaft rides on 30 splines, first gear is 3.06:1, and the case is aluminum with a natural finish paired to a steel pan.

Still need these

A spare speedometer driven gear and housing, carried over from an identical model if you have one, will need to go on since this unit doesn't ship with new ones. There's no shift lever, converter, flexplate, controller, harness, cooler, or fluid included, so treat this as the core unit and build your parts list around it. Sold individually, and it is lockup compatible once wired to a controller, which is worth confirming against your existing wiring before the swap.

Is 550 horsepower a hard limit? Treat it as the advertised ceiling for this build and stay under it for lasting reliability. Does it ship ready to bolt in? You'll still need to add a shift lever, converter, and fluid before it's ready to run.