G56 Transmission

Fully Overhauled G56 Transmissions

No Chinese Gears. No Guesswork.

Every transmission we build uses parts we've personally vetted — not just by brand, but by origin, process, and performance.

We know exactly where every gear, shaft, synchro, and bearing comes from, right down to the factory.

What we’ve learned: no single supplier makes the best of everything.
So we source each component individually from the best available manufacturer — not based on brand, but based on results.

No shortcuts. No compromises. No blind loyalty. Just the best parts, every time.

Why We Love the G56

The G56 is smoother, quieter, and more modern than the older iron-case manuals — and it holds its own when built right.

• Aluminum case keeps weight down and helps with heat dissipation

• Tighter shift feel than the NV5600, especially with a short throw

• Good gear spacing for both daily driving and towing

• Ideal for street-driven Cummins trucks that still see hard work

It’s not as raw as the older stuff, but with a few upgrades, it’s a solid performer — and it shifts like a dream.

For those who want a little more than a standard overhaul has to offer....

• Upgraded synchronizers
• Cryotreated gears
• Cryotreated bearings
• Fast Coolers

Each transmission comes with a 12 month warranty that covers any builder's negligence associated with our work. If there's one thing that sets us apart in this market it is our willingness to stand behind our product. Competitors often refuse to warranty these transmissions even when they clearly advertise a warranty. We get it, it is hard to warranty a transmission intended for high-performance applications that get's abused on a daily basis. However, DON'T ADVERTISE a warranty if you refuse to help anybody that calls in with a problem. 

By making this purchase the customer agrees to send in core. Once the core is received and evaluated RoadRunner transmission will provide an additional estimate if necessary (for transmissions with excess damage). Once the build is completed the finished transmission will be shipped back to the customer. Please email for more information. We prefer to establish contact and set the table with our customers before proceeding with any build. We do not wish to sell you something that you do not need. Thank you