68RFE Ram 3500 Cummins Slipping: Causes and Fix

When a Ram 3500 Cummins comes in "slipping," the first thing I want is the VIN, not the scan tool. The one-ton is the truck where the transmission question is least obvious: depending on year and engine it may not have a 68RFE at all, the software bulletins an owner finds online often belong to the other transmission, and a narrow band of 2024 trucks has a factory hardware bulletin whose fix is a complete transmission. Get those three things sorted and the actual slip diagnosis on a 3500 gets a lot shorter.

This post is the 3500-specific path. The general clutch-by-gear breakdown is in our 68RFE slipping guide, and the tuner and tire side of the story is covered in the Ram 2500 slipping post. Sources are numbered at the bottom.

Recommended 68RFE parts

The parts that fix a slipping 68RFE in a 3500: a friction module for a burned overdrive pack, a heavy-duty valve body for 2019-up trucks with a leaking switch valve bore, and a thermal bypass kit for the heat that started it. Secure checkout.

68RFE High Energy Friction Clutch Pack Rebuild Module

$255.99View part

68RFE Valve Body 2019-Up - Remanufactured Heavy Duty

$1025.00View part

68RFE Thermal Bypass Valve Kit, 2019-2024 Ram 6.7 Cummins

$111.99View part

Step 1: Prove It Is a 68RFE

Ram's 2024 Heavy Duty specification sheet lists the 68RFE behind the standard-output 6.7L Cummins (370 hp, 850 lb-ft) in both the 2500 and 3500. The high-output 6.7L (420 hp, 1,075 lb-ft) is a 3500-only package and gets the Aisin AS69RC. [1] So a 3500 Cummins is never automatically a 68RFE.

The early fifth-generation trucks muddy it further. FCA's NHTSA defect report for recall 22V-835 states that Ram 3500 production with the 68RFE began on September 18, 2019. [3] And FCA's 2019 3500 pickup transmission bulletin, TSB 21-002-21, applies to trucks with either the standard-output (sales code ETL) or high-output (ETM) engine paired with the Aisin AS69RC (sales code DF2). [2] In other words, a 2019 3500 with the standard-output engine can be an Aisin truck. Check the build sheet for sales code DG7 (68RFE) versus DF2 (AS69RC) before you buy a single part. The two units take different fluid, different filters and different hard parts, and nothing in this article applies to the Aisin.

Step 2: Do Not Chase the Wrong Bulletins

Search "Ram 3500 transmission flash" and you will land on a run of TCM reprogramming bulletins. TSB 21-002-21 (2019 3500), TSB 21-021-22 Rev. A (2020 3500 pickup and cab chassis) and TSB 21-019-22 Rev. A (2021) list complaints that sound exactly like a slipping truck: poor shift quality, shift or gear hunting, and "engine flare caused by the transmission releasing the clutch too early during a 1 to 2 shift." [2] Every one of them is written for the Aisin AS69RC (DF2) or AS66RC (DF3). The pickup applicability on 21-021-22 and 21-019-22 is the high-output ETM engine with the Aisin. [2] None applies to a DG7 truck.

On the 68RFE trucks, FCA's software fixes come as PCM flashes. TSB 18-005-23 (January 12, 2023, also RSU 23-007) covers all 2022 Ram 2500 and 3500 Cummins pickups. For DG7 trucks its listed improvements include reducing "audible engine flare during upshifts," helping prevent overdrive clutch premature wear, and fixing 1-2-1 gear hunting on grades under high load in low-traction conditions, with P0755 and P0765 among the DTCs. [2] The labor operation for the 68RFE version, 18-19-04-TG at 0.5 hours, is "Inspect and Reprogram and Perform Quicklearn Routine," versus 0.4 hours for the Aisin trucks. [2] The extra tenth is the Quicklearn. If a 3500 has been flashed for any reason and nobody ran the Quicklearn afterward, do that before you condemn the overdrive pack.

Step 3: Run the VIN for the 2024 Thrust Bearing Bulletin

This one is new enough that a lot of shops have not seen it, and it matters because the codes it sets look like a textbook slipping transmission.

FCA TSB 21-012-25 Rev. B, "Rear Selective Thrust Washer Failure," dated February 21, 2025 and also released as RSU 25-018, covers 2024 Ram 3500 and 2500 pickups with the 6.7L Cummins (ETL) and the 68RFE (DG7) built from June 14, 2024 through September 4, 2024. [2] The truck must have a MIL and one or more of these DTCs:

• Ratio codes: P0731, P0732, P0733, P0734, P0735 and P0729 (gears 1 through 6 incorrect ratio)
• Pressure codes: P0841, P0868 (fluid pressure low), P0871 and P0876
• Others: P0218 (high temperature operation activated), P0716 (input speed sensor performance) and P0944 (loss of hydraulic pump prime)

Owners may also report hard shifts into gear and limp mode. The listed cause is rear selective thrust bearing cracking. [2] The repair procedure is blunt: if any of the listed DTCs are present, replace the transmission (part K52109056AC, a 68RFE that comes prefilled and needs only an ATF+4 top-off, plus six new converter bolts), then perform the Quick Learn. If no DTCs are present, the dealer closes the RSU with a 0.2-hour inspection. The replacement is 3.3 hours, plus 1.0 hour on 4x4 trucks. [2]

For an independent shop, the takeaway is simple. A 2024 3500 in that build window, showing multiple ratio codes with a pressure code on the side, is a warranty transmission, not a clutch job. Check the VIN in the RSU list before tearing anything down.

Step 4: Check the 2019-2020 Valve Body Recall

Safety recall W03 (NHTSA 20V-043) covers about 85,000 2019-2020 Ram 2500 and 3500 pickups with the 68RFE. FCA's dealer instructions describe "a buildup of pressure and heat inside the transmission" that can push fluid out of the dipstick tube. [3] The remedy is a new lower valve body separator plate, check ball and fastener (part package CSKLW031AB), followed by a check that the PCM has current software. [3]

Two reasons this belongs in a slip diagnosis. First, a truck that has been expelling fluid can simply be low, and a low 68RFE will slip under load. Second, a truck that missed W03 is running the old separator plate and possibly old software, so any calibration-related flare has not been addressed either. If the plate has never been changed, do the recall first and re-evaluate.

Step 5: Pin Down the Slip With Ratio Math

With the VIN questions answered, the scan tool work is the same discipline as any clutch-to-clutch unit. Log engine rpm, input speed, output speed, gear commanded, line pressure and transmission temperature on a loaded drive. Then divide input speed by output speed and compare it to the gear ratio.

Per Ram's spec sheet, the 68RFE ratios are 3.23 first, 1.84 second, 1.41 third, 1.00 fourth, 0.82 fifth and 0.63 sixth. [1] A healthy unit in sixth reads very close to 0.63 input-to-output. If that number creeps up toward 0.70 and wanders while the truck is pulling, a clutch is not holding. If the input-to-output ratio is dead on but engine rpm is climbing away from input speed, the gear train is fine and the converter clutch is the one slipping. Those are two very different repairs.

The pattern I see most on one-tons is drift in fifth and sixth only, on a grade, with a trailer. That points straight at the overdrive clutch, which Sonnax notes applies in fifth and sixth. [4] It is also why P0735 and P0729 show up together on these trucks.

Why the 3500 Burns Overdrive Clutches

The 3500 is the truck that spends its life at full load in the overdrive gears. Ram offers it with a 3.73 axle on single and dual rear wheel trucks and a 4.10 on the dually. [1] With a heavy fifth-wheel behind it, the transmission is asking the OD pack to hold through hours of highway pulling, and the OE pack was not built with much margin.

Sonnax scopes its overdrive failure article to the 2007-2020 Ram 2500 and 3500 with the 6.7L Cummins and lists the weak points. The OE overdrive clutches are single-sided, with a steel core only 0.034 inch thick, compared with 0.080 inch for the OE direct clutch steels in a 4L80-E. Thin plates warp under heat, clearance shrinks, and the pack drags and burns. [4] The top of the OE OD housing is unsupported and flexes under apply. Inner retainer wear, worn solenoid switch valve bores that cross-leak OD apply oil, and a solenoid conductor plate that warps under connector seal force all bleed off the pressure the pack needs to hold. [4]

Sonnax ties its switch valve kits to codes 841, 868, 871, 988, 1775 and 1776, and links high line pressure to P0871. It recommends verifying main line pressure with the OE line pressure adapter, tool No. 8259, which replaces the line pressure sensor so you can check pressure and the sensor at the same time. [4] So when a 3500 shows OD ratio drift together with P0868 or P0871, the valve body is a suspect, not just the clutches.

Heat Is the Accelerant

Mike Brown's GEARS column on 48RE, 68RFE and AS68RC overheating is built around a 2008 Ram 3500 6.7L with a 68RFE that ran hot towing a small boat. His usual suspects: a plugged cooler line, a plugged cooler, a plugged internal filter, overloading, engine overheating and a bad fan clutch. He puts the ideal maximum transmission temperature at 200°F and says every 20°F above that roughly halves transmission life. Cooler return flow should be at least one gallon per minute, and if the thermostatic bypass valve is suspect he replaces the cooler as an assembly rather than flushing it. [5]

On a 3500, a slip that only appears after 30 minutes on a grade and disappears after the truck sits is a heat problem until the temperature log says otherwise. Fix cooler flow and the bypass valve before you build a new pack, or the new pack goes the same way. A stock 68RFE that runs hot will also cook its fluid. The 2022 Ram 2500/3500 owner's manual specifies ATF+4 only, calls for the level check at 158-176°F, and schedules a fluid and filter change at 60,000 and 120,000 miles for frequent trailer towing, versus 120,000 miles otherwise. [6] Almost every 3500 qualifies as frequent towing.

The Repair That Holds on a One-Ton

If the truck is outside the RSU windows, the software is current with a fresh Quicklearn, temperature and cooler flow are healthy, and sixth gear still drifts off 0.63 under load, you have a mechanical overdrive failure. On a working 3500, the repair that stays fixed covers the whole circuit:

1. Valve body first. Vacuum test the solenoid switch valve bore and fit the oversized valve and plug if it fails. Check the conductor plate for warp. [4]
2. Overdrive pack and housing. Sonnax's Smart-Tech OD housing holds a taller clutch pack with thicker steels, which Sonnax rates at 20 percent more clutch capacity, and adds a bolt-on anchor plate to stop the flex. [4] On a truck that pulls heavy, that is worth more than another set of OE-thickness frictions.
3. Inner retainer. Inspect for wear; Sonnax lists heavy-duty retainer kits 72554-01K and 72554-11K. [4]
4. Cooler circuit. Flow-test the return, and replace the cooler or bypass valve if it is not moving at least one gallon per minute. [5]
5. Fluid. ATF+4, level set hot, no additives. [6]
6. Quicklearn. After any hard part, valve body or software change, every time. [2]

For capacities and fill procedure, see the 68RFE fluid type and capacity guide and our transmission fluid spec chart.

FAQ

Why is my Ram 3500 Cummins 68RFE slipping in 5th and 6th gear?

The overdrive clutch applies in 5th and 6th, so drift in those two gears under load usually means the OD pack is not holding. Sonnax traces it to thin 0.034 inch OE steels that warp with heat, OD housing flex, inner retainer wear and a worn solenoid switch valve bore that cross-leaks apply oil. Confirm with input-to-output ratio: 6th should read about 0.63.

Does every Ram 3500 Cummins have a 68RFE transmission?

No. Ram's 2024 specifications put the 68RFE behind the standard-output 6.7L only; the high-output 6.7L in the 3500 gets the Aisin AS69RC. FCA's 2019 3500 bulletin 21-002-21 also covers standard-output trucks with the Aisin, and 3500 production with the 68RFE began September 18, 2019. Check the build sheet for sales code DG7 (68RFE) or DF2 (AS69RC).

Is there a TSB for a 2024 Ram 3500 68RFE with ratio codes?

Yes. TSB 21-012-25 Rev. B (RSU 25-018) covers 2024 Ram 2500 and 3500 Cummins trucks with the 68RFE built June 14 through September 4, 2024. With a MIL and codes such as P0729-P0735, P0868 or P0871, the cause is a cracked rear selective thrust bearing and the repair is a replacement transmission plus Quick Learn.

Do the Ram 3500 TCM flash bulletins fix a slipping 68RFE?

Not the 2019-2021 TCM flashes. TSBs 21-002-21, 21-021-22 and 21-019-22 apply to the Aisin AS69RC and AS66RC, not the 68RFE. For 68RFE trucks, FCA's fixes are PCM flashes such as TSB 18-005-23 for 2022, which addresses upshift flare and OD clutch wear and requires a Quicklearn afterward.