The 48RE and 68RFE are the automatics behind two generations of the Cummins in Ram heavy-duty trucks. The 48RE is a four-speed used with the 5.9L Cummins from roughly 2003 to 2007, and the 68RFE is a six-speed introduced with the 6.7L Cummins for the 2007.5 model year. They are not interchangeable without major changes, because the engines, electronics, bellhousings and control strategies differ.
48RE vs 68RFE at a glance
| Factor | 48RE | 68RFE |
|---|---|---|
| Gears | Four forward | Six forward |
| Gear ratios | 2.45 / 1.45 / 1.00 / 0.69 | 3.23 / 1.84 / 1.41 / 1.00 / 0.82 / 0.63 |
| Engine | 5.9L Cummins (common rail) | 6.7L Cummins |
| Shift control | Hydraulic with electronic throttle valve actuator and governor pressure control | Fully electronic with a solenoid pack |
| Fluid | ATF+4 | ATF+4 |
Which is better for towing?
The 68RFE’s deeper first gear and extra ratios keep the engine in its power band and make starts with heavy trailers easier, while its two overdrives lower cruising engine speed. The 48RE is simpler and has a strong following among owners of modified 5.9 trucks, where built versions handle large power increases.
48RE vs 68RFE reliability
Both have known weak points. The 48RE’s include TTVA and governor pressure faults, overdrive slipping and band adjustment; the 68RFE’s include heat when towing, solenoid pack faults and converter shudder. Neither is a clear winner; condition, maintenance and cooling matter more. See 48RE problems and 68RFE problems.
Maintenance differences
The 48RE needs periodic band adjustment and benefits from attention to its throttle valve actuator and governor pressure parts, while the 68RFE has no bands to adjust but relies on its solenoid pack and electronics. Both use ATF+4 and both run hot when towing heavy, so fluid and filter service on the severe schedule and a clean cooler are the most important habits for either; see transmission cooler.
Driving differences
Drivers moving from a 48RE truck to a 68RFE truck notice the extra gears most when pulling a trailer from a stop and when cruising, where the second overdrive lowers engine speed. The 48RE, with only four gears, makes bigger jumps between ratios and leans more on the Cummins’ low-speed torque.
Can you put a 68RFE behind a 5.9?
Not as a simple swap: the 68RFE needs its own control electronics and calibration, and adapting it to a 5.9 truck involves bellhousing, wiring, crossmember and driveshaft changes. Replace like with like for a straightforward repair.
Replacement transmissions
Our StreetMonster 48RE is $4,099.00 and the RoadReady 68RFE is $4,299.00, both with a torque converter. Compare every version on our 48RE and 68RFE pages, and see 68RFE vs Aisin and 47RE vs 48RE.
More guides: Cummins swap transmissions · 66RFE vs 68RFE · how long a 48RE lasts.
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