The steepest first gear ratio of any four-speed automatic (3.06) belongs to the GM 4L60 (700-R4)/4L60-E family of transmissions. The shift from 3.06 ratio (1st Gear) to 1.63 ratio (2nd Gear) is a dramatic RPM drop that causes performance engines to fall out of their power band.

Sonnax 2.84 input carrier kit 77284-K transforms the popular 4L60 series from an OE “wide ratio” 3.06/1.63 to a “close ratio” 2.84/1.55 for game-changing acceleration on the track. This keeps performance engines in the optimal power band while allowing a longer pull in first and second gears, improving consistency and performance. Learn more about the benefits of this ratio change.

Manufactured and engineered for outstanding durability, the carrier's gears are precision-ground to OE standards, thrust washers feature highly wear-resistant PTFE-coated material and the captured bearing is thicker late design. Lube channels direct oil to the pinion pins, and the carrier can be disassembled for inspection and service.

• Keeps engine in power band on 1-2 and 2-3 shifts
• Delivers longer pull in 1st and 2nd Gears
• Six-pinion planet loaded with advanced durability features
• No special tools or machining required