Turbo 400 Heavy Duty Duty Forward Drum Input Shaft Volume Spacer Sonnax Set

The ideal GM TH400 upgrade for any power level, Sonnax heavy duty forward drum 34554-01 features a unique combination of high-strength, light weight and a cutting-edge design to optimize transmission performance.

Racing applications quickly push the heavy, cast-iron OE drum over its limits, with failure most common at the weak point where the shaft and drum connect. The problem can be addressed with a larger spline and lighter-weight, aftermarket aluminum drum, but durability becomes a huge issue with wear of the clutch splines, shaft spline connection and seal ring bore.

To dramatically reduce weight and deliver the ultimate in reliability, the Sonnax high-strength, chromoly steel drum is custom-engineered with several lightening features for a low rotating mass. It weighs 3 lbs less than the OE drum and is just 3 oz. heavier than a common aluminum drum. Weight is reduced carefully, without compromising strength, by ribbing the front of the drum, adding clutch splines (28 vs. 14) and lightening holes, plus reducing the diameter inner section of the drum at the middle seal ring area.

This versatile drum upgrade has an oversized 28-tooth shaft-to-drum spline and can be used with a variety of input shaft styles. This includes Sonnax 1" dia., 30-spline heavy duty input shaft 30280-02, Sonnax 1-1/8” dia., 35-spline big input shaft 35280-02 and other aftermarket shafts with 28-spline connection between shaft and drum.

• Ultra-modern drum delivers both high-strength and light weight for unrivaled performance at any power level
• Compatible with Sonnax and other aftermarket 28-spline input shafts
• Optimized for use with rubber clutch separators for applications with clean neutral setups
• Clutch spline major diameter is reduced slightly, and two sets of full-length clutch splines added to back up clutch separators
• Lightening holes correspond to input speed sensor locations in aftermarket cases for more accurate converter and shift data
• Middle seal is eliminated — an aluminum clutch volume spacer kit34554-11K  for applications where clutch fill/drain time may be a concern
• Sonnax high RPM checkball capsule57510-01 is installed to eliminate pressure drop at high (5500+) RPM — a common problem with OE and other aftermarket checkballs

Input shaft failure is a common problem in performance GM TH400 transmissions running with added horsepower. OE and aftermarket shafts simply don’t hold up in these conditions, leading to spline twist and shaft breakage.

Sonnax heavy duty input shaft 30280-02 is ideal for any street or strip application where maximum durability is needed from a stock-size, 1" dia. shaft. It is manufactured from 300M high-strength steel with additional processing for resistance to fracture.

This shaft is intended for use with aftermarket converters with internal turbine support, and its Forward drum spline is designed to be used with Sonnax heavy duty forward drum34554-01 or other aftermarket drums with compatible 28-tooth spline.

• High-strength 300M steel shaft undergoes additional processing to build-in resistance to fracture
• Ideal for high horsepower street/strip applications running 1" dia. input shafts