The sonnax shift improvement module consists of three Tricumulator™ springs, designed for late ’95 and up Ford Trucks using E4OD, 4R100 Automatic Transmission (where no short inner springs were used). This is by far the only shift improvement you will ever need! And “A Must For Every Rebuild ". The springs increase the line pressure in the transmission to firm up the shifts and make them happen faster.
Feel seat of the pants performance from your sluggish transmission!

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Sonnax now offers the line pressure modulator sleeve and valve kit, which eliminate this oil loss problem with closely-held tolerances.
The sleeve has been manufactured out of carbon steel and the valve from hardened alloy steel to prevent excessive wear.
The sleeves have an O-ring added, similar to the AX4N style, to help prevent excessive EPC oil loss.
The valves incorporate annular grooves to properly center the valve in the sleeve and eliminate side loading, which can lead to excessive wear.
The outside diameters of the sleeves are the same, so the kits may be used in either of the E4OD, 4R100 or AX4N.