In this issue of fishing for the facts, we’ll take a look at a 2016 Ram 2500 equipped with a 6.7L Diesel and a 68RFE transmission that was experiencing torque converter clutch concerns. I was at home last week and received a phone call from my good buddy Tom, who had just gotten back from a weekend fishing tournament where he won first place and was excited to call and share his weekend with me. During the conversation, Tom mentioned that he was experiencing overheating of the transmission and a vibration concern while driving. The next weekend, I decided to ride over to Tom’s house to see if we could duplicate his transmission overheating and vibration concern.
BASS, BUMPS, AND A BAFFLING CONCERN
After arriving at Tom’s house, I inspected the vehicle to make sure that everything was okay. We began by checking the fluid levels. Fluid levels were good at this time. We then connected our pressure gauge to the transmission so we could monitor the pressure while driving. We also connected our scan tool to the data link connector (DLC) so we could monitor the vehicle’s operation while driving. Now that the scan tool was connected to the DLC and the pressure gauge was connected to the transmission, it was time to head out for our initial road test to see if we could duplicate his concerns.
HOOK, LINE, AND DIAGNOSTICS
On our way to the freeway, everything seemed to be okay. The transmission temperature seemed to be normal, and there was no vibration at this time. After driving at freeway speeds for a while, the transmission temperature began to increase from 195° to 230°, and the TCC slip was increasing. As the torque converter slip increased, we started to feel a vibration sensation. Now that we had duplicated the overheating and vibration concerns, it was time to head back to the shop and diagnose them further.
BACK AT THE SHOP: THE DISSECTION BEGINS
Back at the shop, we used our thermal gun to verify the operation of the transmission temperature sensor, and at this time, the sensor was accurate. We monitored cooler flow to make sure we were getting a minimum of one gallon per minute; the cooler flow was okay. We used a thermal gun to verify the temperature drop across the cooler. The temperature drop across the cooler was within specifications, indicating the cooler was capable of doing its job. We accessed the PCM to check for codes and found code P0740 (TCC out of range).
With overheating and vibration confirmed, and P0740 detected, we installed a pressure gauge on the damper release port to monitor the TCC release pressure (Figure 1). While monitoring the TCC release pressure, we noticed that the TCC release pressure was higher than normal at 20 psi, which should be five psi or lower. We also installed a pressure gauge in the damper apply port to monitor TCC apply pressure. We noticed that the TCC apply pressure was low with a reading of 85 psi, indicating an internal hydraulic leak. TCC apply pressure should match the actual line pressure of 120 psi. At this time, we pulled the pan and found torque converter debris in the pan. With torque converter debris in the pan, it was time to remove the transmission for an inspection. With the transmission on the bench, we disassembled the transmission to inspect the pump, valve body, and torque converter. We found that the solenoid switch valve in the valve body (Figure 2) and the torque converter accumulator piston in the pump (Figure 3) were worn. 
We performed a vacuum leak test to determine the extent of valve wear. It is recommended to hold a minimum of 18 inches of vacuum. The vacuum during the test would not hold and dropped to zero quickly. Now that we have confirmed the problem, it’s time to make the repair.
DTC TROUBLESHOOTING: P0740 – TCC OUT OF RANGE, SET CONDITION
The transmission must be in EMCC mode with input speed greater than 1750 rpm. The L/R TCC solenoid achieves the maximum duty cycle and can not pull the engine speed within 60 rpm of input speed. Additionally, when the transmission is in the FEMCC mode and the engine slips TCC by more than 100 rpm for 10 seconds, the DTC P0740 will be set. This DTC can take up to five minutes to identify the problem before illuminating the MIL.
DTC TROUBLESHOOTING < P0740 – TCC OUT OF RANGE > THEORY OF OPERATION:
When the transmission is in 2nd gear through 6th gear, the torque converter clutch (TCC) can be engaged under certain conditions. The TCC piston is electronically modulated by increasing the duty cycle of the L/R-TCC solenoid until the torque converter slip difference (difference between the engine and transmission input speed) is within 60 rpm. Then the L/R – TCC solenoid is fully energized (FEMCC – 100% duty cycle), and torque converter slip is monitored in FEMCC to ensure adequate clutch capacity.
BENCH DIAGNOSIS: WORN AND WEARY PARTS
We repaired the solenoid switch valve in the valve body and the torque converter accumulator valve in the pump using kits from an aftermarket supplier. After repairing the torque converter accumulator in the pump and the solenoid switch valve in the valve body, it was time to reassemble the transmission, install a new torque converter, and reinstall it in the vehicle.
A 50-MILE TEST DRIVE AND THE ROAD TO REDEMPTION
With the transmission and new torque converter installed in the vehicle, it was now time for the road test. With transmission up to operating temperature and fluid levels correct, we installed our scan tool to the DLC connector. We cleared all codes and performed our relearn procedures. We installed our line pressure gauges on the damper release and apply ports. We then headed out to the highway for a good, long test drive to monitor Transmission temperature and TCC operation as well as transmission performance. While heading to the highway, the transmission operation, TCC slip, and transmission temperature were within specification, as monitored by all gauges and the scan tool. Traveling on the highway, we decided to take a 50-mile round-trip road test to monitor TCC slip, overheating conditions, and feel any vibration. While the first 25 miles were a success, we decided to return to the shop to complete our work. Back at the shop, it was time for a recheck of the operation. No codes were present, and the transmission temperature was within specifications. We checked our fluid levels, checked for leaks, and uninstalled our pressure gauges and scan tool. Tom was very satisfied with the performance and operation of his vehicle. He was now ready for his next fishing tournament and a great weekend adventure. And that, my friends, is what we call Fishing for the Facts.
