GM's Baby Duramax Diesel: Tiny Crankshaft Wiggle Could Mean Big Trouble in 2026

0-liter straight-six diesel. That engine, nicknamed "Baby Duramax," is now the subject of Technical Service Bulletin (TSB) 25-NA-307, addressing thrust bearing wear that can let the crankshaft move too much.

That movement, called "end play," can destroy internal oil seals, send metal debris through the oil system, and ultimately ruin the engine's bottom end. Owners on Reddit report hearing metallic scraping, knocking, or a rapid rattle from the bell housing area, sometimes before the first oil change, often under 10,000 miles.

In severe cases, the damage requires a full long-block replacement, not just a bearing swap.

The TSB notes the acceptable crankshaft end play is 0.084-0.316 mm, roughly the thickness of a piece of paper to a playing card. Exceed that, and you may also see diagnostic code P06DD, rough idle, hard cranking, or low oil pressure warnings.

This is a TSB, not a safety recall. That means GM isn't obligated to contact all owners or offer free repairs unless symptoms appear. The suspected cause may be a batch of early crankshafts with manufacturing or material issues, failing under high-load events like towing in heat or hard launches.

A revised crankshaft and thrust bearing are in the works, but as of December 2025, backorders run up to four months. 89 for gas, per the latest DOE data. 2-liter V8, with the same 13,300-pound towing capacity.

Looking ahead, GM's next-gen trucks will keep the TurboMax four-cylinder as the base engine, currently the most reliable option in the lineup, while the Duramax gets updated parts to fix this crank-wiggle issue.