This is the reference email — everything covered in this sequence in one place. Bookmark it, forward it to the guy in your shop who works on RAM trucks, or pull it up the next time someone asks you what fluid goes in a 68RFE. This is the distilled version of what I've covered across this entire Dodge/Chrysler/RAM sequence. 68RFE — 6-speed automatic behind the 6.7L Cummins in RAM 2500 and 3500, 2007–present. The heavy-duty diesel truck transmission. Known for overdrive clutch pack weakness under high-torque and towing loads. Fluid: Mopar ATF+4. 45RFE / 545RFE — Chrysler-family units used in RAM 1500 (pre-2013 with Hemi), Durango, Grand Cherokee, and Dakota. The 45RFE is 4-speed; the 545RFE adds a 5th gear. Known for governor pressure solenoid failure (P0745). Fluid: Mopar ATF+4. NAG1 / 722.6 — Mercedes-licensed 5-speed used in 300C, Charger, Challenger, Magnum, and Jeep Grand Cherokee with Hemi, SRT, and diesel engines, 2003–2011. Known for output speed sensor failure (P0720) and solenoid switch valve issues (P1776). Fluid: Mopar ATF+4 in Chrysler applications — not Mercedes 236-series. ZF 8HP (8HP70 / 8HP75) — ZF-manufactured 8-speed used in RAM 1500 (2013+), Challenger, Charger, and Jeep Grand Cherokee with Hemi and EcoDiesel. Fluid: Mopar ZF 8&9 Speed ATF (ZF LifeguardFluid 6 spec). Not ATF+4. This is the most common service error on the ZF platform in Chrysler vehicles.
Recommended Products
Mopar ATF+4
Search AmazonThe foundational fluid for 68RFE, 45RFE, 545RFE, and NAG1 applications. Every diagnostic sequence in this guide starts here. If you own a RAM 2500 or 3500 diesel, keep 8 quarts on hand. If you own a Hemi RAM 1500 (pre-2013) or a 300/Charger/Challenger, keep 6 quarts. Fresh ATF+4 resolves more Chrysler transmission complaints than any other single service.
Check Price on AmazonBlueDriver Bluetooth OBD2 Scanner
$89.95The scanner that makes this entire guide actionable. Reads Chrysler-enhanced codes across all platforms — 68RFE, 45RFE, 545RFE, NAG1, and ZF 8HP. Pulls sub-codes under P0700, reads live TFT, governor duty cycle, TCC slip, and line pressure. Every diagnostic step in the sequence above requires enhanced code access and live data. This is the one tool every Dodge, RAM, and Chrysler owner should own.
Check Price on AmazonLucas Oil Transmission Fix
$14.87The low-cost supplement that earns its place in a fresh ATF+4 service on any 68RFE, 45RFE, or 545RFE showing TCC shudder, harsh engagement, or early slip codes. Reconditions valve body seals and TCC clutch surfaces during the relearn cycle. Add to the drain-and-fill service as the first response to any fluid-related symptom before committing to parts replacement.
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