Transgo SK 722.6-A Shift Kit, 722.6 / W5A-580 / NAG1

This is the TransGo SK 722.6-A, a valve body correction kit for the Mercedes 722.6 five-speed automatic and its Chrysler-badged twin, the NAG1 (also called the W5A-330 on smaller engines and the W5A-580 on the larger ones). The 722.6 ran behind a huge range of Mercedes cars and vans from the late 1990s through the 2000s, and the same box shows up as the NAG1 in the Chrysler 300, Dodge Charger, Challenger, Magnum, Jeep Grand Cherokee, and the Dodge/Freightliner Sprinter. These units are known for pressure-related complaints as the aluminum valve body bores wear.

The kit targets the exact circuits that give trouble. It includes a drop-in USA-made hardened pressure regulator valve cut with longer lands, so it rides on previously unused areas of the bore and restores line pressure without machining the housing. A new lube pressure regulator valve with its own bushing, spring, and sleeve brings the lube circuit back into spec using the existing worn bore. You also get three overlap regulator valve bushings and replacement springs for the control pressure regulator and the 2-3 shift pressure valve, which are the two springs that commonly break inside these valve bodies.

On the bench, the job goes in with the valve body off the transmission. A tech drops the valve body, works through the specific bores the instructions call out, installs the new hardened valve and bushings, swaps the two problem springs, and reassembles. Plan on two to three hours the first time and go slow on the spring plate bolts, which are soft and strip easily. No sublet machine work is required.

Reach for this kit when a 722.6 or NAG1 flares on the 2-3 shift, is slow to build line pressure, slips or shudders through the torque converter clutch, or sets code 053, P0740, or P0741. It is a preventative upgrade as well, worth installing any time the valve body is already out during a service or rebuild. New kit, ships from the USA, handling in 1-2 business days.