Technical Teardown: Inside The New Cummins ZF 8-Speed Transmission

The Cummins diesel engine has a legendary reputation for making massive power, but the question has always been whether the transmission behind it can keep up.

In a recent YouTube video uploaded by Randy’s Transmissions, one of their mechanics, Nick, tore down the new ZF 8-speed transmission to see if it’s finally a worthy match for the iconic diesel.

The teardown revealed a surprisingly robust unit with some key upgrades in all the right places.

Inside the New Cummins ZF 8-Speed Transmission

The teardown began with Nick noting the modern, but sometimes frustrating, features of the new transmission. Like many new units, it’s heavy, lacks a dipstick, and uses a plastic oil pan with an integrated filter.

Once inside, he found a modern mechatronic system that combines the computer and solenoids into the valve body. One of the first major differences he noted was a remote, chain-driven oil pump, an uncommon design for the shop.

A Look at the Core Components

Digging deeper, Nick found a mix of familiar and beefed-up parts. The planetary gear sets, he noted, were nearly identical to those found in other ZF 8-speed applications.

However, the B-clutch pack was impressively beefy and included anti-drag wave rings, a thoughtful feature designed to keep the clutches from dragging after they release.

The main drum was also noticeably thicker and stronger than the versions found in lighter-duty ZF transmissions, showing that ZF clearly engineered this unit for heavy-duty torque.

A Major Upgrade Where It Counts

The real surprise came when Nick got into the clutch drums. He explained that the ZF 8-speeds used in high-horsepower cars like the Hellcat have a known weak point: an aluminum E-clutch drum that can fail.

In this new truck version, ZF has upgraded that critical component to a much stronger steel drum right from the factory.

The change addresses a major concern for performance enthusiasts and builders. “I am fully surprised on how well they built these units,” Nick admitted during the teardown.

ZF 8-Speed Transmission: A Strong Foundation For The Future

After completely disassembling the new ZF 8-speed transmission, Nick’s final verdict was overwhelmingly positive.

“I have to tell you, I am very impressed that Cummins decided to throw a transmission behind their powerplant to actually hold up,” he concluded.

While the stock unit is strong, the team at Randy’s is already developing upgraded clutches and steels to increase its holding capacity even further for high-performance builds. As Nick put it, “We’re going to make some things better for you guys.”