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

View Instructions

Engine power and RPM continue to increase, creating the need for different transmission and axle ratios to get the car down the track as quickly as possible. The innovative Sonnax 1.58 ratio Extreme planetary assembly kit 28158G-06SP 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 different transmission.

Extreme planetary assemblies from Sonnax include Advanced Process sun gears and pinions made to the same exacting standards used on Formula 1, Nascar and other high-end professional racing circuits. Advanced Process parts undergo an additional three-step process that allows for greater durability and higher levels of performance. These units are fully assembled and ready to install.

  1. Cryogenic tempering to ultra-low temperatures (-350°F) for an even denser, more uniform gear with a tough and wear-resistant structure.
  2. Shot peening for increased gear resistance to fatigue failure, cracking or galling.
  3. Super-finish to reduce friction, vibration, noise and wear on the gear, potentially tripling the life of the part.

The 1.58 assembly's front and rear sun gears undergo an additional Dry Film Lubricant (DFL) treatment to reduce spalling and improve longevity. The carrier also includes high strength steel/bronze/PTFE-coated rear sun gear washer and pinion thrust washers.

  • High-strength 300M output shaft with “rolled splines” to prevent spline twist
  • Direct replacement, requires no special assembly or case modification
  • Sonnax Extreme 9310 Advanced Process gears
  • Bolt together carrier for ease of service
  • High capacity reverse clutch assembly included

I’m definitely pleased with the 1.58 gear set. It’s the right combination for the car and ran all season with no transmission trouble. Great product.

S. Fisher Fisher & Kolivas Arkansas

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 Warrenton, VA

The 1.58 gear set has had a significant impact on helping my racing program this year and played a big part in our being able to win two races and be more competitive. It has enabled us to have a much greater tuning window and allowed us to apply the power from the engine more efficiently. The 1.58 has over 50 passes on it and is still going strong. Thank you to Sonnax for making such a great product and for developing new transmission parts so that we as racers can continue to improve and go faster.

K. Ashley Kevin Ashley Racing Newark, DE

The attention to detail on the 1.58 gear set was very impressive including coatings, metal finish (agma spec), thrust washer design/coatings, center washer design/coatings and the newly designed oil feed system which I feel is the key to its success. At the 30 pass interval the transmission was examined and the gear set was found to be in "untouched" condition. I can say with confidence that this product contains state of the art designing and anyone who decides to purchase one will be very happy with the results and durability of this product.

J. Hutchinson Hutch’s Transmission Service London, Ontario

Sonnax's 1.58 is not just the lowest numerical Powerglide ratio...it is the highest quality Powerglide gear we have ever seen!

M. Yow Torque Trends, Inc. Arizona

Requires one of the following Sonnax 24-tooth high gear clutch drums: 28756-01, 28756-08, 28756-01K, 28756-08, 28756-15K or 28756-16K.

  • Gear Process Level: Extreme
  • Material: 300M Rolled Spline
  • Shaft Length Option: Short
  • Flange Tooth Count: 24
  • Ratio: 1.58

  • 28165g 06sp