The NAG1 — Mercedes-Benz designation 722.6 — is a 5-speed automatic that Chrysler licensed from Mercedes and used in a range of applications from roughly 2003 through 2011. You'll find it behind the 5.7L Hemi and 6.1L SRT Hemi in the 300C, Charger R/T, Challenger, Magnum, and Jeep Grand Cherokee, as well as behind the 3.0L diesel in the Grand Cherokee CRD. It's a well-engineered transmission that handles torque well — but it has its own service requirements that differ from the Chrysler-native units, and those differences catch owners off guard. The NAG1 in Chrysler applications uses Mopar ATF+4. This is one of the points of confusion — the 722.6 in Mercedes vehicles uses a different fluid specification (Mercedes 236.x series), but Chrysler respecified the NAG1 for ATF+4 in their applications. Do not use Mercedes-spec fluid in a Chrysler NAG1 unless specifically directed by a current service bulletin — the hydraulic system was revalidated for ATF+4, and using Mercedes 236 series fluid creates a mismatch in viscosity and friction chemistry the same way Dexron does. Mopar ATF+4. Full stop.
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Mopar ATF+4
Search AmazonRequired fluid for the NAG1/722.6 in all Chrysler, Dodge, and Jeep applications. The first step in any NAG1 diagnostic sequence — P0720, P0730, P1776 — is verifying ATF+4 spec and condition. Pick up 6 quarts for a drain-and-fill. Do not substitute Mercedes-spec fluid or Dexron in a Chrysler NAG1 application.
Check Price on AmazonBlueDriver Bluetooth OBD2 Scanner
$89.95Reads Chrysler-enhanced codes on NAG1 applications including P0720, P0730, and P1776 — plus sub-codes under P0700 that identify specific solenoid or circuit faults. Live data includes output speed sensor signal and TFT, both critical for diagnosing the most common NAG1 failure patterns. Works on 300C, Charger, Challenger, Magnum, and Grand Cherokee NAG1 applications.
Check Price on AmazonLucas Oil Transmission Fix
$14.87Add to a fresh ATF+4 service on a NAG1 showing P0730 or P1776 where fluid condition is the suspected cause. Helps recondition valve body seals and hydraulic passages that have been running contaminated fluid. Add as a supplement to the fluid service — not a standalone treatment — before committing to solenoid pack or valve body replacement.
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