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A shift flare is the engine RPM climbing for a moment during a shift instead of dropping cleanly into the next gear. On a 68RFE behind a Cummins you usually feel it first on the 2-3 or 3-4 upshift with a load on, or on a 3-2 kickdown when you are passing a semi on a grade. The truck feels like it took its foot off the clutch for half a second, then it catches, sometimes with a bump.
Here is the blunt part: a flare means one clutch released before the next one was holding. That is either a hydraulic problem (pressure, solenoid, valve body, fluid) or a friction problem (the clutch pack is worn and needs more volume to apply than the TCM expects). Hydraulic problems can be fixed with the transmission in the truck. Friction problems cannot. Your whole job in diagnosis is figuring out which one you have before you spend money.
The Shift That Flares Tells You Which Clutch Is Involved
The 68RFE is clutch-to-clutch: the TCM releases one clutch and applies another with timed solenoid control, so the shift that flares points at the clutch involved. Common RFE-family pairings:
- 2-3 flare: the 2C clutch releasing and the OD clutch applying. OD is the classic 68RFE wear item on tuned trucks.
- 3-4 flare: the UD clutch releasing and the 4C clutch applying.
- 4-5 flare: the 4C clutch releasing and the 2C clutch applying.
- 3-2 or coast downshift flare: the TCM has to time a release and re-apply against engine braking, so pressure control and solenoid response matter as much as friction condition here.
Confirm against the service manual for your year, but if every shift into one clutch flares, start there.
Step One: Fluid Level, Done Right
We have seen more 68RFEs "fixed" by a quart of ATF+4 than by any part in this guide. A low unit pulls air into the pump on hard stops and grades, aerated fluid compresses, and clutch apply goes soft.
- Bring the transmission up to normal operating temperature. A cold check reads low and people overfill.
- Park on level ground, engine running, foot on the brake, cycle through every gear, then return to Park.
- Read the dipstick against the hot range. If your scan tool shows transmission temperature, use it.
- Look at the fluid. Dark, burnt smell, or flakes of friction material on the stick means the clutches are already cooked.
If the fluid is overdue, a pan drop with a fresh 68RFE filter kit ($30.99) is cheap insurance. Look at what is in the pan. Fine gray paste is normal. Black friction material and bright metal are not.
Step Two: Scan Tool and Clutch Volume Index
Do not throw parts at a 68RFE without a scan tool that reads Chrysler TCM data. The number that matters most is the clutch volume index (CVI). The TCM learns how much fluid volume it takes to fill each clutch (L/R, 2C, OD, UD and 4C) and stores it. As frictions wear and clearance grows, the volume needed goes up, and so does the CVI.
Pull the CVI values and compare them against the specification in the service manual for your model year. A clutch reading at or past the top of its range, or one that is far higher than the others relative to spec, is your slipping clutch. If they keep climbing after a quick learn, the friction is going.
Also pull codes. The ratio codes are P0731 (gear 1), P0732 (gear 2), P0733 (gear 3), P0734 (gear 4) and P0735 (gear 5) incorrect ratio. Any of them means slip. Line pressure codes in the P0867-P0869 range point at the pressure sensor or pressure control side, and solenoid or pressure switch circuit faults show up in the P07xx and P08xx families. A ratio code with no electrical codes leans toward friction.
The Usual Suspects
Solenoid Pack (TRS / Solenoid Block)
The 68RFE solenoid and pressure switch assembly bolts to the valve body and controls every clutch apply. Solenoids get slow and pressure switches fail, usually intermittent and worse hot. On 2007.5 through 2018 trucks the 68RFE solenoid pack ($181.99) is the most common in-truck fix we see. 2019-up trucks use a different unit, the 2019-up 68RFE solenoid pack ($502.99).
Line Pressure, Input and Output Sensors
The TCM controls line pressure in closed loop off the line pressure sensor. A sensor that reads high makes the TCM cut pressure, and you get soft, flaring applies. The input/output and pressure sensor kit ($59.99) is cheap enough that we replace them as a set when the data looks suspicious.
Valve Body Wear and Accumulators
Bore wear in the valve body leaks apply pressure. Accumulator pistons and their cover plates are a known weak spot on the RFE family, and a leaking accumulator softens the apply on the clutch it cushions. The accumulator piston and reinforced plate kit ($100.99) addresses that directly. If the valve body is worn out, a remanufactured 2010-2018 68RFE valve body ($405) is less work than rebuilding yours.
A shift kit like the 45RFE/545RFE/68RFE shift kit ($133.99) firms up applies and corrects factory hydraulic weak spots. Good on a healthy transmission; no cure for burned frictions.
Engine Tuning
This is the big one on Cummins trucks. A tune that adds a lot of torque without matching transmission tuning asks the stock clutch packs to hold more than they were sized for, and the TCM's stock shift pressures do not know about it. The OD and 4C clutches usually show it first. If the flare started after a tune, add transmission tuning that raises pressure and shortens shift times, or turn the power down.
Symptom to Fix: Quick Reference
| Symptom | Likely Cause | Fix | Parts Cost |
|---|---|---|---|
| Flare comes and goes, worse on hard stops or grades | Low or aerated fluid | Check level hot, top off, service filter | $31 |
| Flare started after battery, fluid or parts work | Adaptive values reset or wrong | Quick learn with scan tool | $0 |
| Intermittent flare, worse hot, solenoid or switch codes | Solenoid pack / pressure switch | Replace solenoid pack | $182-$503 |
| Soft shifts everywhere, line pressure codes | Line pressure sensor or pressure control | Replace sensors, check pressure | $60 |
| Soft apply on one clutch, CVI normal | Accumulator or valve body leak | Accumulator kit, shift kit, or reman valve body | $101-$405 |
| One clutch CVI high and climbing, ratio code | Worn clutch pack | Rebuild with new frictions | $227-$256 module, plus kit |
| Flare only after a power tune | Torque past clutch capacity | Transmission tuning or less power | Varies |
Quick Learn: When It Helps and When It Does Not
Quick learn is a scan tool procedure that resets the TCM's clutch fill adaptives and has it relearn them. It is required after a solenoid pack, valve body or transmission replacement, and it is worth doing after a battery disconnect or a tune change.
What quick learn cannot do is make a worn clutch hold. If the flare goes away after a quick learn and comes back in a few hundred miles with the CVI climbing, you just confirmed a friction problem.
Repair vs Rebuild
If the fluid is clean, CVI values are within spec, and you have electrical or pressure codes, fix it in the truck. A solenoid pack, sensors and a quick learn is a weekend job.
If the fluid is burnt, there is friction material in the pan, or one clutch CVI is out of range and climbing, the transmission is coming out. Do not put a solenoid pack on a slipping unit and call it fixed. On the bench, the BorgWarner 68RFE friction clutch module ($226.99) or the high-energy friction clutch pack module ($255.99) covers the frictions. Tuned or towing, go high-energy. A full shop rebuild, including labor to pull and install the transmission on a Cummins Ram, typically runs several thousand dollars, which is why catching it early with the CVI matters.
68RFE Parts, Ships Same-Day
Solenoid packs, valve bodies, clutch modules, sensors, filters and shift kits for 2007.5-up Ram Cummins trucks. For complete rebuild kits and hard parts, our sister store Core Transmission Parts carries the full line.
Shop 68RFE Parts →FAQ
Will a quick learn fix my 68RFE shift flare?
Only if the flare started right after a battery disconnect, a fluid service, a solenoid pack or valve body swap, or a tune change. Quick learn resets the adaptive clutch fill values so the TCM can relearn them. It cannot make a worn clutch pack hold. If the flare returns within a few hundred miles, the hardware is the problem.
Does a 68RFE flare set a code?
Often not at first. The TCM keeps adapting until it runs out of room. When the slip gets bad enough you will see gear ratio codes such as P0732, P0733, P0734 or P0735, and the transmission may drop into limp mode in second gear.
Can low fluid cause a 68RFE to flare?
Yes. A 68RFE that is even a little low will aerate the fluid under load and on hard stops, which makes clutch apply pressure inconsistent. Check the level hot, engine running, in park, before you buy any parts.
Is a shift kit a fix for a 68RFE flare?
A shift kit corrects valve body and accumulator weak spots that cause soft, slow applies. It is a good fix when the clutches are still healthy. It does not repair burned frictions, and putting one on a slipping transmission just hides the problem for a while.
How much does it cost to fix a 68RFE flare?
Parts for the common fixes run from about $31 for a filter kit to $182 for a solenoid pack, $405 to $1,025 for a remanufactured valve body, and roughly $227 to $256 for a friction clutch module. A full shop rebuild on a Cummins 68RFE typically lands in the several-thousand-dollar range once labor is included.