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The 68RFE behind the 6.7 Cummins is a strong transmission in stock form for an empty truck. The trouble is nobody buys a Cummins to drive it empty. Hook a fifth-wheel to it, run it up a grade in overdrive, and the factory overdrive clutch pack is the part that pays the price. The OD pack is undersized for the torque a loaded Cummins makes, and it is the number one 68RFE failure that lands these trucks on the bench.
The failure follows a predictable arc, which is good news, because if you know the symptoms you can catch it while it is still a clutch job and not a complete teardown full of metal.
Symptoms, In the Order You'll Feel Them
- Slip in overdrive under load first. Towing up a grade in 6th, the RPM flares and the truck loses ground. Empty it feels fine, loaded it slips. That is the OD pack starting to let go.
- Flare on the shift into overdrive. The engine revs on the 5-6 shift before it catches, then settles. Worsens as the frictions glaze.
- Harsh downshift / bind, then loss of OD. Eventually it drops OD entirely and holds a lower gear, or it bangs in and out.
- Burnt fluid, dark color. Pull the dipstick. OD clutch material in the fluid smells burnt and darkens the ATF+4.
- Codes P0871, P0846, P0731, P0700. OD pressure/ratio codes that confirm the pack.
Why the OD Pack Burns Up
1. It is undersized for the load
The stock OD clutch count and friction material were specced for a transmission that does not get hammered loaded all day. Tow heavy and the pack runs hotter than it can shed, glazes, and slips. This is the root cause on most failures.
2. Marginal line pressure under load
The 68RFE relies on its pressure control and the pump to clamp the packs. As the pressure control solenoid and the pump wear, apply pressure sags right when the pack needs it most, accelerating the burn.
3. Heat from inadequate cooling
Stock cooling is borderline for sustained heavy towing. A loaded Cummins generates serious trans heat, and heat is what kills the frictions.
The Fix That Actually Tows
If you tow, do not just put the stock pack back in. The fix that lasts upgrades the weak spot:
| Part | Why |
|---|---|
| Upgraded OD clutch pack (extra clutch / billet) | More frictions and higher-energy material to handle Cummins torque while towing. |
| Master rebuild kit | Replace all seals and the other frictions while it is apart. |
| Updated / upgraded solenoid pack | Restores clean pressure control so apply pressure does not sag. |
| Billet input / intermediate shaft (heavy tow) | The other known weak link if you make big power. Cheap insurance for a tow rig. |
| Aux cooler + fresh ATF+4 | Keeps fluid temp in range so the new pack survives. |
Flush the cooler and lines thoroughly. Burned OD clutch debris hides in the cooler and will glaze a fresh pack fast if you leave it in there.
68RFE Clutch Packs & Solenoid Packs, Same-Day Ship
gearboxinsider.com stocks 68RFE overdrive clutch packs, upgraded solenoid packs, billet shafts, and master rebuild kits built for towing. Order before 2pm Eastern and it ships same day.
Shop 68RFE Parts →Tools and Fluid for the Job
- ATF+4 transmission fluid
- Heavy-duty trans cooler
- Snap ring pliers
FAQ
Can I fix the OD clutch without pulling the transmission?
No. The OD pack is internal. The trans comes out and gets split. Budget the labor or the bench time accordingly.
Is it worth upgrading if I do not tow heavy?
If you genuinely run empty, a quality stock-replacement pack is fine. The moment you tow regularly, the extra-clutch upgrade pays for itself the first summer.
What about a tune that holds higher line pressure?
A trans tune that raises apply pressure and firms shifts helps the pack live, but it is not a substitute for upgrading an undersized pack. Do both for a serious tow truck.