1.58 Ratio Extreme Planetary Assembly Kit
Part No. 28158G-06SP

View Instructions Find a Distributor

Sonnax offers complete GM Powerglide planetary assemblies in a variety of gear set options and configurations to ensure you get the performance you want without overpaying or sacrificing quality. Each comes fully assembled and ready to install.

Track-proven to 3,000 HP, Sonnax Extreme planetaries are the finest quality Powerglide planetary assemblies in the world. From carrier and output shaft to gears and thrust washers, every component is refined for maximum durability in the most demanding applications. The ring gears are even pre-drilled for the Sonnax stabilizer system to prevent vibration and broken reverse friction plates. Extreme gear sets feature Sonnax premium sun and pinion gears that also undergo the same advanced processing used in Formula 1, NASCAR® and other high-end professional racing circuits.

1.58 ratio Extreme planetary assembly kit 28158G-06SP delivers tunable control right at the start, when traction can make or break a race. The one-of-a-kind Sonnax 1.58 is designed to fit into existing Powerglide cases, allowing racers to achieve the lowest numerical ratio available for the Powerglide without the hassle and expense of converting to a TH400.

  • Direct replacement, requires no special assembly or case modification
  • Top-quality sun and pinion gears undergo additional advanced processing for unmatched durability
  • Extreme strength output shaft delivers unrivaled performance and reliability
  • Compatible with the Sonnax big input shaft system to handle the most extreme horsepower
  • Includes high-capacity reverse clutch assembly
  • 24-Tooth billet drum flange designed to work exclusively with Sonnax clutch drums
  • Bolt-together carrier for ease of service

See chart and specs below to determine if this planetary assembly suits your application, or dial in options here to choose your build.


Track-Proven to 2,000 HP


Track-Proven to 3,000 HP

Sonnax Warranty 2 Years (Gears Only) 2 Years (Gears & Shaft)
Gear Material 9310 Suns & Pinions 9310 Suns & Pinions
Gear Process Premium
Advanced (Learn More)
Shaft Material 4340 300M
Shaft Splines Cut Spline Rolled Spline
Drum Flange 12-Tooth 24-Tooth
Ring Gear Standard Maximum Duty

Applies to planetary assembly kits only

  • Carrier Assembly & Output Shaft Short Length, 300M Shaft
  • Front Sun Gear & Drum Flange 24-Tooth
  • Ring Gear
  • Reverse Clutch Piston with Seals 2 Seals
  • Reverse Clutch Piston Plate
  • Reverse Clutch Pressure Plate
  • Reverse Clutch Frictions (7)
  • Reverse Clutch Steels (8)
  • Gear Process Level: Extreme
  • Shaft Length Option: Short
  • Shaft Material: 300M
  • Ratio: 1.58
  • Flange Tooth Count: 24

  • Powerglide 1.58 Ratio Extreme Planetary Assembly Kit 28158G-06SP


From the Bench: Building a World‑Class Powerglide Racing Transmission

The mere fact that we didn’t have to invest a huge sum of money into building a transmission is one of the biggest benefits…and it goes without saying that the new 1.58 gear set has far exceeded our expectations. It has given us the ability to keep the front end on the ground, consistent A-B passes…and the confidence that we have gained with the reliability and consistency of the gear set is priceless.

C. Pechie
Pechie Racing