Dodge RM400 Parts & Accessories

Dodge RM400 Parts & Accessories

The Dodge RM400 is the heaviest configuration in the R-series medium-duty conventional cab lineup, designed for maximum payload and commercial durability. These trucks were built with heavy-duty front and rear axles, stout leaf spring suspension, and big-block V8 engine options capable of sustained heavy work. Today's RM400 owners are typically restorers, fleet maintainers, or collectors keeping a proven commercial workhorse in service.

Popular Upgrades

The most-requested parts for the RM400 include heavy-duty replacement leaf spring packs, brake drums and shoes, wheel cylinders, and master cylinders. Exhaust manifolds and gaskets for the 360 LA V8 and 400 big-block are frequently needed given the age of surviving examples. Carburetor rebuild kits, fuel pump replacements, and ignition system upgrades are also popular, as the original fuel and ignition systems on trucks this old benefit significantly from refreshed components.

Performance & Handling

The RM400 was available with the 360 LA V8 and the 400 big-block B-series V8, giving it substantial towing and hauling capability by any era's standards. The 400 B-series engine shares many parts with the 383 and 440 Magnum, broadening aftermarket options for performance intake manifolds, carburetor upgrades, and cam profiles. The heavy-duty front axle and rear axle benefit from quality replacement bearing, seal, and U-joint hardware to maintain the tight tolerances these trucks need under load.

What engine did the Dodge RM400 come with?

The RM400 was offered with the 360 LA V8 as the base powerplant and the 400 cubic inch B-series big-block as an upgrade option. The 400 B-series shares its block and many components with the 383 and 440, making performance upgrades and rebuild parts widely available. Always verify your engine code via the data plate before ordering rebuild components to ensure correct head gasket, piston, and cam specs.

Are heavy-duty suspension parts available for the RM400?

Yes, heavy-duty leaf spring packs, U-bolts, shackles, and shock absorbers for the RM400 are available through commercial truck parts suppliers. Many suspension components overlap with the D400 and W400 series, expanding your sourcing options. Upgraded spring rates are available for owners who want to restore or exceed original payload capacity after years of commercial use.

Black Ops Auto Works stocks a wide range of Dodge commercial and performance truck parts. Browse exhaust systems, suspension components, and Mopar parts and accessories for your RM400 build.