6.7 Cummins Lifter Failure: What Years Are Affected (And Possible Fixes)

The Cummins 6.7L turbo diesel engine entered its fifth generation in 2019. In addition to improved output of up to 400 horsepower and 1,000 pound-feet of torque, the new engine's valve train featured hydraulic roller lifters compared to the fourth-gen version's solid flat tappet lifters. While the flat tappet design required periodic valve lash adjustments and produced some ticking noises from under the valve cover, it left little room for failure. The hydraulic roller lifters used by the fifth-gen 6.7 eliminated the need to adjust valve lash and reduced the engine noise level, but introduced a new failure point.

Lifter failure in 2019 and newer 6.7 Cummins turbo diesel engines can occur within the first 10,000 miles. Symptoms include a ticking noise on start-up akin to that of typing on a typewriter, especially during cool weather when the engine oil is thicker. Catastrophic failure will throw engine codes, cause the engine to emit smoke from the exhaust pipe, and result in loss of power.

While other automakers have used hydraulic roller lifters with fewer issues, one problem with the Cummins design is the omission of needle bearings in the roller assembly. The roller at the end of the lifter makes contact with the camshaft, rolling around the cam lobes. The lack of needle bearings and tight clearances between the lobes and rollers can release metal shavings into the engine oil or generate excessive heat.

Using the correct viscosity engine oil is key to staving off lifter failure. Stellantis, the owner of Ram Trucks, issued a Technical Service Bulletin (TSB) in July of 2023, stating that 2019 model year and newer Rams need 10W-30 engine oil, while 2018 and older trucks should get 15W-40 oil. The TSB goes on to explain the reasoning behind the recommendation is "due to the new designed valve train," and that using the thicker oil "will cause deposits to form in the Hydraulic Valve Lash Adjusters leading to undesirable noise, and/or engine damage."

Another point of concern for 6.7 Cummins hydraulic roller lifters is a dowel pin used for keeping the lifters aligned. While the issue might sound similar to the Cummins Killer Dowel Pin problem that affected a large portion of 5.9L Cummins engines, they are not related. However, a misaligned lifter can result in catastrophic engine failure.

While using the correct engine oil type and viscosity for the fifth-gen 6.7 Cummins as suggested in the Stellantis TSB is a step in the right direction, at best it reduces the chances of lifter failure with no guarantees of eliminating the problem. However, many Ram truck owners are sufficiently happy with the 6.7-liter Cummins to justify swapping out the hydraulic roller lifters for solid lifters. Lifter conversion kits for the 6.7-liter Cummins diesel aren't cheap, though. Wagler makes a Cummins 6.7 lifter Conversion/spacer Kit that sells for $1,400 and up depending on the vendor. The kit includes new pushrods, adjustable rockers, and lifter spacers designed to replace the stock components. 

There's also a conversion kit from Hamilton Cams, which is priced at about twice the cost of the Wagler kit. It comes with a forged camshaft, tappets, pushrods, and rocker arms. To install either kit without removing the engine, you'll need the DNR Customs magnetic cam removal kit, which will set you back another $499. Neither kit is easy to install in or out of the truck, so you'll want to budget plenty of time and thoroughly research the process before beginning a valve train swap. But when you're done, you won't have to worry about those problematic hydraulic lifters any longer.