A New Trick in the Bag: Additional Second-Gear Servo Size for the 4L60-E

Gregg Nader

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For years we have known the 4L60 and 4L60-E 2nd gear servo came in three different sizes, and one aftermarket size in the Sonnax 2nd gear super hold servo kit 77911-03K. All of these servos have a “proper” apply to release ratio and accommodate a cushion spring. With the 2007 4L70-E, there is now there is a fourth OE servo size that gives builders a new choice when looking for something with increased performance.

The 8642553 casting used in V6 and V8 applications is by far the most common size we see. However, if you are looking to add "a little extra" to a heavy duty rebuild and want a little more 2nd band apply area, but the Corvette or larger aftermarket servo are just too much for a daily driver, try the new 4L70-E servo. This is available from the dealer for about $40.00. You will need to order two part numbers, 24230441 piston & 24229157 divider/housing.

Compared to the Corvette servo, the 4L70-E servo is a modest increase in size over the V6/V8, 8642553 casting servo, and it will not change the shift feel as dramatically as a Corvette or a larger Sonnax 2nd gear super hold servo would. There are plenty of options to change shift feel and upgrade this common transmission. This new 4L70-E servo is one more part you can add to your bag of tricks.


The four OE 4L60 second gear servos are in the top row and divider rings are in the lower row. The ring represents the apply area on the second gear piston. The smaller the inner hole on the ring, the greater the second gear apply area.

Gregg Nader is a Sonnax Technical Specialist and a member of the Sonnax TASC Force® (Technical Automotive Specialties Committee), a group of recognized industry technical specialists, transmission rebuilders and Sonnax Industries Inc. technicians.
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