Runaway Throttle on 2003 to early 2007 Dodge

2500 & 3500 with 5.9L Cummins Diesel Pickups

 

      2003 thru early 2007 Dodge Diesel Pickups may experience a runaway engine after the gear shift is placed in the drive position. A very scary situation when it happens to you. The engine RPM's have been known to reach 3000 to 3500 RPM's and the driver is trying to hold the truck back with the brakes! This ONLY pertains to the 48RE transmission, not the 46or 47RE transmission's.

  This has been a difficult problem for some trying to pinpoint the cause of the problem. Most are misled to believe that the problem is with the diesel engine but it's not! It's caused by the Lockup torque has 1 of 2 problems. Either the sprag/roller clutch inside the converter has failed (marked in red in the pic below) or the lockup  o-ring has cut a groove in the inside diameter of the lockup piston (shown in 2nd pic below). Explanation of the cause below.

48RE Dodge Diesel 2003 up Torque Converter

 

48RE Converter Lockup Piston Grooved 

The 48RE model had several changed in the valvebody to allow the lockup torque converter to be applied in 1st gear under certain conditions. Failure of the lockup torque converter cause the lockup clutch piston to partially apply pulling the motor down when the shifter is placed in Drive/overdrive position. The computer see's the motor RPM's dropping so it gives the engine more fuel so as to not allow the motor to die, this can cause the RPM's to jump up un-expectedly giving the driver a scare. Depending on the number of miles & the condition of the transmission pan when it's removed for inspection if a complete overhaul is required or just the converter is replaced.