6L80, 6L90 300mm Heavy-Duty Converter Builds: Breaking Down the Basics

GM 6L80 and 6L90 transmissions are a hugely popular units found in a variety of vehicles, from gas pickup trucks to diesel fleet vehicles to Corvettes to hotrod Cadillacs. The stock-size, 300mm torque converter is a critical weak point, and Sonnax multi-plate performance converter kits for the JMBX, JMBV, JMDZ and JMDY coded units make it easy to maximize reliability for the ultimate heavy-duty build.

Know Your Build: Performance vs. Heavy-Duty​​​​​​​

Performance: A 6L80/90 “performance” build typically means changing to a smaller diameter converter for a higher stall speed (ex. dropping from a stock-size 300mm to 265 or 258mm).

Heavy Duty: An upgraded 6L80/90 300mm converter is better described as a “heavy-duty” build because there’s no change in size for a higher stall speed. You’re just swapping key OE components for much stronger, more durable parts.

Sonnax offers top-quality converter upgrades for both performance and heavy-duty 6L80, 6L90 applications. Search this chart for the converter kit that fits your needs.