68RFE Ram 2500 Cummins Slipping: Causes and Fix

A Ram 2500 with the 6.7L Cummins and a 68RFE that "slips" is one of the most common tickets in a diesel transmission shop, and one of the most often misdiagnosed. A fair share of the trucks we see have already had a fluid service, a tuner reset or a set of frictions, and they still flare. The reason is that on this truck there are four things that feel like a slip from the driver's seat: an actual clutch letting go, the converter clutch slipping, a PCM calibration that flares the upshifts, and a tune or tire package asking the box for more than its hydraulics can give. Only one of those is fixed with a clutch pack.

This post is the Ram 2500-specific sequence I use before anybody pulls the transmission: what the factory bulletins say about flare and overdrive clutch wear on these trucks, what a tuned or re-tired 2500 does to line pressure and cooler flow, how the towing service schedule plays into it, and how to close the job so it does not come back. If you want the clutch-by-gear breakdown, we cover that in the general 68RFE slipping guide. Sources are listed at the bottom.

Recommended 68RFE parts

The parts that fix a slipping 68RFE on a Cummins 2500: a friction module for a burned OD pack, a valve body for a cross-leaking switch valve bore, and a cooler bypass kit for the heat that started it. Secure checkout.

68RFE High Energy Friction Clutch Pack Rebuild Module

$255.99View part

68RFE Valve Body 2010-2018 - Remanufactured 5-Ball, Standard Duty

$405.00View part

68RFE ZeroStat Cooler Bypass Kit, Ram 2500/3500 6.7 Cummins

$174.99View part

First, Write Down What Kind of Slip It Is

Before the scan tool goes on, get the complaint pinned down on a road test, loaded if the customer tows. The questions that matter on a 2500:

• Which shift or gear? A flare on the 1-2, 2-3 or 3-4 upshift is a different animal from rpm creeping up while cruising in 5th or 6th.
• Empty or loaded? A truck that only slips with a trailer behind it is telling you about holding capacity and heat. A truck that flares empty is telling you about calibration, adaptives or apply pressure.
• Hot or cold? Slip that shows up after 30 minutes of towing on a grade, and goes away after the truck sits, is a heat problem until proven otherwise.
• Stock or modified? Ask directly about tuners, tire size and axle ratio. On a three-quarter-ton Cummins, a large share of repeat 68RFE failures are modified trucks.

Then log engine rpm, input shaft speed, output shaft speed, gear commanded, TCC slip, line pressure (desired and actual), line pressure duty cycle and transmission temperature. If input-to-output ratio holds while engine rpm runs away from input speed, the clutches are holding and the converter clutch is slipping. GEARS magazine warns specifically that excessive TCC slip on this unit is easy to mistake for a flare on the 4-5 shift, and it ties that slip to wear in the torque converter regulator valve bore in the pump. [5]

Check the Software Before You Check the Clutches

Ram has released PCM calibrations that target exactly the complaints a 2500 owner calls "slipping." Two bulletins worth knowing:

TSB 18-005-23: flare on upshifts and OD clutch wear

FCA bulletin 18-005-23, dated January 12, 2023 (superseding 18-094-22 Rev. B and also released as RSU 23-007), covers 2022 Ram 2500 and 3500 pickups with the 6.7L Cummins (sales codes ETL and ETM). For trucks with the 68RFE (sales code DG7) its listed conditions include an audible engine flare during upshifts, improvements to help prevent premature overdrive clutch wear, and 1-2-1 gear hunting on grades under high load in low-traction conditions. Transmission DTCs on the list include P0755 (shift solenoid B) and P0765 (shift solenoid D). The cause is listed as PCM software. [1]

The important part for anyone working on these trucks is in the repair procedure: after the PCM is reprogrammed, a 68RFE truck gets the transmission Quicklearn routine (it even has its own labor operation, 18-19-04-TG at 0.5 hours, versus 0.4 hours for the Aisin trucks). Flash without the Quicklearn and you have a new calibration running on old clutch-fill data. [1]

TSB 18-067-25: ratio codes and overheat derate

TSB 18-067-25, dated July 24, 2025 (superseding 18-019-24 and released as RSU 25-146), covers the 2022 Ram 2500 with the 6.7L Cummins, sales code ETL. The truck must have a MIL with one or more of P0868 (transmission fluid pressure low), P0933 (hydraulic pressure sensor range/performance), P0735 (gear 5 incorrect ratio) or P0729 (gear 6 incorrect ratio). The owner may also report a transmission overheat message on the cluster, a check engine light that comes and goes, and 68RFE sump temperature derate. Again the cause is PCM software, and the repair is an inspect-and-reprogram. [2]

Notice what those codes are. P0735 and P0729 are exactly the ratio codes you would expect from a slipping overdrive clutch, because the OD clutch is applied in 5th and 6th. On a 2022 truck, a 5th/6th ratio code with a P0868 or P0933 alongside it is a software check before it is a teardown. If the truck is on the RSU list and is already at the latest level, the bulletin tells the dealer to close it and do normal diagnosis, which is your cue that the problem is real hardware. [2]

For any model year, the rule is the same: confirm the PCM is at the latest calibration with wiTECH, and if it is not, flash it, Quicklearn it and road-test it again before you condemn anything mechanical.

The Quicklearn Is Part of the Repair, Not an Option

The 68RFE learns how long it takes to fill each clutch and adjusts its shift timing from that. Change anything that affects fill time, such as frictions, steels, clearances, a valve body, a solenoid pack or the PCM software, and the old learned values are wrong. The result is a flare on the shift the TCM thinks it already knows how to do. Sonnax puts it flatly in its RFE overdrive troubleshooting article: after any repair to these units, perform a fast learn. [3]

Use the dealer routine (FCA's bulletin points to Service Info Section 08, Electronic Control Modules, Module, Transmission Control, Standard Procedure, Quicklearn) with the fluid at operating temperature and the level correct. [1] Then drive it easy for a while so adaptives can settle before the customer hooks up a fifth wheel. Owners with tuners should know that every PCM flash, stock or custom, is a reason to redo the Quicklearn.

Tunes, Tires and Line Pressure on a 2500

This is where three-quarter-ton trucks part ways with the half-ton world. A Cummins 2500 is very often tuned, lifted, on 35-inch tires, or all three. Each of those raises the pressure the TCM commands, and on the RFE family more line pressure does not mean more holding power for free.

What the scan data looks like

GEARS gives the healthy numbers at idle in Drive: about 60 to 70 psi commanded and actual, with the line pressure duty cycle around 22 to 24 percent. A commanded duty cycle of 18 percent or higher shows the control has margin. Below 10 percent is unsuitable for this transmission, and a duty cycle pinned at 5 percent with actual pressure below desired means the pump cannot keep up. [5] At steady cruise on flat ground, a duty cycle that sits at or trends toward 5 percent tells you the unit is working too hard, and GEARS notes an aggressive tune or oversized tires can command around 225 psi in 6th gear. [5]

Why high pressure starves the converter and cooler

Sonnax measured what tuning does at the pressure regulator. On a stock unit at a stop in Drive, line pressure is 60 to 70 psi at a 22 to 24 percent duty cycle and cooler flow is about 1.3 GPM. On a tuned unit, idle line pressure was 100 to 105 psi at a 5.1 percent duty cycle, and cooler flow dropped to about 0.5 GPM, and to 0.3 GPM at maximum pressure. [4] The cause is valve position: pushed that far over, the pressure regulator leaves only a small undercut feeding the converter, cooler and lube circuits. Less converter charge means more TCC slip; less cooler and lube flow means heat in the clutch packs. That is a slip and burn-up on a truck whose clutches were fine when the tune went in.

The fixes are in the valve body and the drivetrain, not in a thicker friction. Sonnax's 44912-17K lube-regulated pressure regulator valve gives line pressure a direct path to lube and, per Sonnax, about 60 percent more lube and cooler flow at maximum line pressure than the OE valve. [4] GEARS adds that a line-to-lube orifice of 0.055 to 0.062 inch is the alternative on high-performance builds (not on a case already drilled for one), and is blunt that oversized tires without a regear keep failing units no matter how well they are built. [5]

Heat, Towing and the Service Schedule

A 2500 Cummins that pulls a trailer is on the severe service schedule whether or not anybody told the owner. Ram's diesel supplement calls for a 68RFE fluid and filter change at 60,000 miles for frequent trailer towing, against 120,000 miles otherwise, and has the level checked hot at 170 to 180 F on the 68RFE. ATF+4 only, with no additives. [6] The same owner information describes TOW/HAUL mode resetting to normal at every key cycle and recommends using the Electronic Range Select to cut down on shift hunting and heat buildup when towing. [6] A driver who forgets TOW/HAUL on every trip is cycling the 5-6 shifts on grades all day.

Check the fluid on the stick, then look at it. Dark, burnt-smelling ATF+4 with clutch material on the stick means a pack has already been slipping. A service will not fix it, and on a truck that has gone well past 60,000 miles of towing without one, there is a good chance the overdrive clutch is the next stop. If the truck runs hot in the logs, check the cooler circuit and the thermal bypass before you blame the pack.

When It Really Is the Overdrive Clutch

If the software is current, the Quicklearn has been done, line pressure and cooler flow are healthy and the input-to-output ratio still drifts in 4th, 5th and 6th, you have a mechanical OD failure. Sonnax scopes its OD failure article to the 2007-2020 Ram 2500 and 3500 with the 6.7L Cummins and names the weak points: single-sided OE steels with a 0.034 inch core that distort with heat, an OD housing whose unsupported top flexes under apply, inner retainer wear that causes drag, solenoid switch valve plug wear that cross-leaks OD apply oil, and a solenoid conductor plate that can warp and bleed pressure. [3] Sonnax lists the switch valve plug kits against codes 841, 868, 871, 988, 1775 and 1776, so a P0868 or P0871 next to OD slip points at the valve body as much as the clutches. [3]

A repair that holds on a working 2500 addresses all of it at once: vacuum test the switch valve bore and fit oversized parts if it fails, set clutch clearances to spec (too tight shortens fill time and can bind up, too loose drags and overheats), check the OD dribbler valve, put in the frictions and steels, and consider the reinforced OD housing on a truck that tows or is tuned. [3] Then do the Quicklearn. Frictions alone on top of a leaking switch valve bore will come back in the same condition.

The Order I Work a 2500 Slip Complaint

1. Road test and log: which gear, loaded or empty, hot or cold. Separate TCC slip from clutch slip using engine, input and output speed.
2. Fluid: level checked hot, condition and smell, service history against the 60,000-mile towing interval.
3. Software: check for open bulletins and RSUs (18-005-23 and 18-067-25 on 2022 trucks), flash if needed, Quicklearn, retest.
4. Modifications: tune, tire size, axle ratio. Read duty cycle at idle and at cruise.
5. Heat: transmission temperature in the logs, cooler flow and bypass valve.
6. Hydraulics: line pressure against the gauge, switch valve bore, TCC regulator.
7. Hard parts: OD clutch, housing, steels. Quicklearn after the repair, every time.

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

FAQ

Why does my 68RFE Ram 2500 Cummins flare between shifts?

On many trucks it is calibration or adaptives, not a worn clutch. FCA TSB 18-005-23 lists an audible engine flare during upshifts on 2022 Ram 2500 and 3500 Cummins trucks with the 68RFE and fixes it with a PCM flash followed by the transmission Quicklearn. Check for current software and redo the Quicklearn before condemning the clutches.

Do I need to do a Quicklearn after flashing or tuning a 68RFE?

Yes. FCA's bulletin calls for the Quicklearn on 68RFE trucks after the PCM is reprogrammed, and Sonnax says to perform a fast learn after any repair to these units. Without it, the transmission runs a new calibration or new parts on old clutch-fill data and flares.

Can a tuner or bigger tires make a 68RFE slip?

Yes. Sonnax measured a tuned unit idling at 100 to 105 psi with a 5.1 percent duty cycle and cooler flow down to about 0.5 GPM, against 1.3 GPM stock. Less converter charge and lube flow means more converter slip and hot clutches, and GEARS warns that oversized tires without a regear keep failing these units.

How often should the 68RFE fluid be changed on a 2500 that tows?

Ram's diesel supplement calls for a 68RFE fluid and filter change at 60,000 miles for frequent trailer towing, versus 120,000 miles otherwise. Use ATF+4 only, with no additives, and check the level hot at 170 to 180 F.