48RE Over Shifts from 3rd to Overdrive with Converter Lockup then Back to 4th

[BZFlyer]

Hi Everybody,

I have a 2006 Dodge 5.9L Sport 4WD 4door auto with the 48RE, a nice truck.  Now at 145,000 miles and 30,000 miles on a rebuilt transmission from Randy's in Tooele UT, behind a 425 hp (max) engine rebuild by Industrial Injection.  Edge tuner.  Mall crawler from day one.

Occasionally with very little acceleration out of 3rd, the transmission will over shift to overdrive, then immediately downshift to 3rd.  Never did that before the rebuild, or just after the rebuild.  Just a problem for the past year and 10,000 miles.  No other transmission service after the rebuild.  Coming up on tranny rebuild warranty expiration. 

My tuner and transmission show 4 gears plus overdrive.  The transmission starts in 1st, then you can feel a shift to second at about 13mph, then 3rd at about 25mph, then 4th at about 35mph, then what feels like an extra gear at about 45 mph.  My tuner shows gears 1-4 plus a 'lock' symbol once in overdrive.

The transition from 3rd to lock up, than back to unlocked overdrive 4th gear, is intermittent and typically will occur after some driving (warmed up?) and at about 35-37mph with little acceleration.  So apparently the transmission is just on the verge of shifting 3-4, but goes directly from 3 to 4 lockup, then decides that's not right, and shifts back to 4th unlocked.

To clarify the truck's equipment, the VIN without the serial number portion is:  3D7KS28C46G------.

Bill
 

[Moses Ludel]

Bill…Your VIN is straightforward.  Like my ’05 3500 4WD, your 2006 was built at Saltillo, Mexico.  Your GVWR is 8,001-9,000 lbs. (mine is higher).  The truck is a “Heavy Duty” 2500 4x4 Quad-Cab that came with the “H.O.” 5.9L Cummins.  in 2006, these trucks had a G56 manual six-speed or our 48RE automatic transmission.  

The 48RE is derived from the A727 3-speed with a planetary overdrive built into the unit behind the band apply planet assemblies.  The architecture is similar to the A518, A618, 46RE and 47RE.  The 48RE is the last and beefiest version with improved planetary pinions from the factory.  Randy’s would use these planetary units or a heavier duty design for its high horsepower build.

You have a total of four speeds forward.  4^th gear is overdrive.  There is no “5^th gear/overdrive”.  There is, however, a lock-up converter that you may feel after the shift to 4^th gear.  If the transmission remains in 4^th/overdrive when the Edge tuner indicates “LOCK”, the tuner may be locking the converter and transmission in overdrive during that mode. 

I have a manual lockout that prevents the transmission from up-shifting from 3^rd to 4^th/overdrive when I climb grades.  This holds the transmission in 1^st-2^nd- 3^rd gears and prevents the engagement of 4^th/overdrive.  You should have a similar factory mode to hold down in 3rd under heavy loads.  “Haul” or “Tow” mode is the factory language.  Your gear selector's 3rd gear position (as opposed to "D") will serve that function.  My 2005 did not come with an overdrive lockout selection.  I resorted to a BD Overdrive Lock-Out switch, specifically designed for 2005 Ram 48REs.  Your 2006 does not need an aftermarket switch, you simply shift to "3", and the transmission will not shift up to 4th/Overdrive.

The ratios in a 48RE are spaced wide between 3^rd (1:1) and overdrive (0.69:1).  This is a 31% overdrive ratio in 4^th gear.  The lock-up of the converter could feel like another “gear” shift if Randy’s uses a firm locking converter.  The tuner may be showing 1-2-3-4 plus lock-up of the converter.  The 48RE is considered a 4-speed with 4^th being the over-driving gear. 

You can clarify the ratios and gears with Randy’s;  however, they likely use the factory 1-2-3-4/Overdrive ratios built into the planetaries.  I visited the Randy’s website and confirmed your list of upgrades.  (Like Randy's, I have installed several Sonnax pieces in my 48RE transmission, and it hasn't been on the bench at 183,000 miles.) 

I also went to the Edge site and find it interesting that they sell a 2003-2012 Ram in-cabin tuner under one part number.  Apparently, they use the same tuner for 48RE and 68RFE transmissions.  The 68RFE is a 6-speed used from mid-2007 up with the 6.7L diesel.  6^th gear is overdrive.  The instructions that came with your tuner may help clarify the “gears” and “LOCK” mode indicated.

When the converter locks up in any gear, the ratio for that gear remains the same.  Lock-up simply eliminates slippage at the torque converter.  When the converter locks up in 4^th/overdrive, the overdrive ratio remains the same.  The speed-up (slight) that you feel is from elimination of the converter slip.  Think of 4^th gear as a legitimate gear.  Though separate from the front planetary assemblies that use the bands, the overdrive planetary and its clutch plates create a distinct ratio change just like each of the other gear ratios. 

You can think of the converter lock-up as members of the converter no longer being allowed to slip (a percentage).  Slip is a normal function of torque converters without lock-up.  Lock-up converters came about to meet emissions and fuel efficiency standards.  They typically lock up at a designated road speed and throttle pressure, unlocking at lower speeds to allow smooth shifts and a normal engine idle. 

If you have a manual lockup or tow/haul control, when shifting into this mode, even in lower gears, you will feel the converter lock up to eliminate slip, accompanied by a slight rise in engine rpm with that lock up.  Again, that can feel like a slight “gear” change but is simply the converter members locking and no longer being allowed to slip.

So, to your question...You're indicating that the transmission goes briefly into 3rd then up-shifts to 4th/Overdrive plus lock-up.  Then the converter uncouples, which feels like a shift.  After reaching a higher road speed, the overdrive/4th gear once more goes into lock-up mode of the converter.  

Are you getting any P-codes?  If check lights are still functional after the upgrade transmission, here are several of the codes that can occur if a fault like you describe is serious enough to "hard set" a code.  I'm listing these to provide a conceptional framework for transmission related electrical and electronic malfunctions.  Also included is the Throttle Valve or TVVA, which also can be a source of trouble and erratic shift points.  Poor electrical connections, a defective governor solenoid or a TVVA either out of calibration, defective or with a loose connection can each create erratic shift points or premature torque converter (TCC) lockup:

AUTOMATIC TRANSMISSION 48RE DIESEL ELECTRICAL DIAGNOSTICS
DIAGNOSIS AND TESTING
P0711-TRANS TEMP SENSOR, NO TEMP
RISE AFTER START (DIESEL)
P0712-TRANS TEMP SENSOR VOLTAGE
TOO LOW (DIESEL)
P0713-TRANS TEMP SENSOR VOLTAGE
TOO HIGH
P0720-LOW OUTPUT SPEED SENSOR -
RPM ABOVE 15 MPH (DIESEL)
P0748-PRESSURE SOL CONTROL/TRANS
RELAY CIRCUITS (DIESEL)
P0850-P/N SWITCH PERFORMANCE
(DIESEL)
P0868-GOVERNOR PRESSURE SENSOR
P0869-GOVERNOR PRESSURE SENSOR
VOLTS TOO LOW (DIESEL)
P0882-TRANS 12 VOLT SUPPLY RELAY
CONTROL CIRCUIT LOW 
P0883-TRANS 12 VOLT SUPPLY RELAY
CONTROL CIRCUIT HIGH (DIESEL)
P0973-TRANSMISSION OVERDRIVE
CIRCUIT VOLTAGE TOO LOW (DIESEL)
P0974-TRANSMISSION OVERDRIVE
CIRCUIT VOLTAGE TOO HIGH (DIESEL)
P1740-TCC O/D SOL PERFORMANCE
(DIESEL) 
P1749-TRANSMISSION THROTTLE VALVE
POSITION SENSOR CIRCUIT LOW 
P1750-TRANSMISSION THROTTLE VALVE
POSITION SENSOR CIRCUIT HIGH 
P1751-TRANSMISSION THROTTLE VALVE
POSITION MINIMUM RANGE
PERFORMANCE 
P1752-TRANSMISSION THROTTLE VALVE
SPAN PERFORMANCE 
P1753-TRANSMISSION THROTTLE VALVE
MECHANICAL PERFORMANCE 
P1754-TRANSMISSION THROTTLE VALVE
ACTUATOR STUCK
P1755-TRANSMISSION THROTTLE VALVE
CONTROL CIRCUIT 
P1756-GOV PRESS NOT EQUAL TO
TARGET @ 35 - 40 PSI (DIESEL) 
P1757-GOV PRESS ABOVE 3 PSI IN GEAR
WITH 0 MPH (DIESEL) 
P1762-GOV PRESS SENSOR OFFSET
VOLTS TOO LOW OR HIGH (DIESEL) 
P2769-TRANSMISSION TCC CONTROL
CIRCUIT LOW
P2770-TRANSMISSION TCC CONTROL
CIRCUIT HIGH (DIESEL) 
 

You did not mention any thrown codes.  Considering the vehicle's speed around the 3rd to 4th shift and lock-up, I would focus here and also on the transmission temperature or temp sensor.  The transmission's factory temperature sensor sees 260-degrees F as the tipping point.  If the transmission gets hotter than this, the 4th gear/overdrive is disabled and 3rd gear with TCC (torque converter lock-up) is engaged.  The intent here is to increase transmission fluid flow to help cool the transmission. 

Is this problem occurring in the summer only, when the transmission might be heating up?  Do you have a temperature gauge on the transmission?  Many performance transmission builders recommend use of a permanently mounted/installed transmission temp gauge and often an add-on transmission cooler.  The factory coolers can clog and create overheating of the transmission.

Another consideration is the normal road speed for the TCC function or lock-up of the converter.  You share that this problem occurs at 37 mph.  Depending upon variables like stock axle gearing, modified axle gearing, oversized tires and so forth, the transmission's governor function, TVVA pressure/calibration, vehicle speed sensor and TCC solenoid could trigger a premature lock-up of the converter.  Each of these issues requires a scan tool to monitor the functions during a test drive when the erratic shift and lockup symptom occurs.

The most common problem sources are poor electrical plug connections.  TCC circuit connections, controller connections and even the Edge tuner's wiring to the chassis/powertrain can cause voltage fluctuations.  If the problem persists, I would check the electrical connections and grounds related to the transmission's shifting and include wiring from the tuner to the truck's electrical system.  Factory wiring is generally more reliable than aftermarket splice-ins.

Moses