In this issue of “Keep Those Trannys Rolling”, we’re going to take a look at a 2017 Ford F150 Raptor that was experiencing a “rumble” sensation at times while driving.
Our 2017 Ford F150 Raptor is four wheel drive and is equipped with a 3.5l twin-turbo Eco-boost engine and a 10R80 transmission. We first encountered this vehicle when the customer contacted us complaining about a rumble type sensation while driving at times. The customer stated that the rumble sensation was very intermittent and would usually only occur during light throttle driving and also that the “ck engine” would illuminate at times and then go out.
As always, before heading out for the initial test drive, we inspected the vehicle for any obvious concerns, such as dirty corroded battery terminals, loose wiring or connections. We inspected the air intake system and air filter for restrictions. We checked the transmission fluid level and condition. The transmission fluid level was correct and the fluid was clean and red. We installed our scanner and checked for codes.
There were no current hard fault codes at this time. However, there were two memory codes stored in the TCM. These codes were 741 and 1744 (TCC performance) and possibly indicated a torque converter clutch system concern. We cleared the codes out of the TCM memory, left the scanner connected to the DLC connector and headed out for our initial test drive to see if we could duplicate the customer’s concerns.
TEST DRIVE TO DUPLICATE:
With the scanner connected to the DLC connector, we headed out for our initial test drive to see if we could duplicate the customer’s concerns. While driving the vehicle, we monitored the engine load inputs, such as mass air flow (MAF), manifold absolute pressure (MAP), throttle position sensor (TPS), the last downstream oxygen sensor, transmission shift commands and torque converter clutch operation.
We drove the vehicle through city streets, ranging from 15 mph to 35 mph and on the highway at highway speeds. The vehicle seemed to work perfectly. Just as we were getting ready to head back to the shop, we pulled into a grocery store parking lot to make a U-turn. As we started moving through the parking lot at approximately 5-10 mph, we felt a low speed rumble sensation when the transmission made a 1-2 shift at light throttle. During the low speed rumble sensation, we continued to monitor the engine load sensors and the last downstream oxygen sensor operation.
The engine load sensors and the last downstream oxygen sensors were working properly, which indicated we were not looking at an engine performance problem. We checked the transmission commands on the scanner and found that the rumble sensation occurred during the 1-2 shift while the torque converter clutch was being commanded on.
We monitored the torque converter clutch slip and found that the torque converter clutch slip was increasing while the rumble sensation was occurring. This was an indication that the torque converter clutch slip was causing the rumble sensation during light throttle operation. With the rumble sensation duplicated, it was time to head back to the shop and diagnose this concern.
TORQUE CONVERTER CLUTCH CONTROL SYSTEM:
While monitoring the torque converter clutch slip during the rumble sensation and verifying that we were experiencing a torque converter clutch slip concern, it was time to take a look at the torque converter clutch control system.
The torque converter clutch control system consists of:
- Torque Converter
- Stator Support System
- Valve body-TCC regulator valve
- TCC solenoid
- Transmission Control Module (TCM), including wiring and connections
- Engine Performance sensors- (maf, map, tps, vss, ect, tft)
The torque converter clutch system is controlled by the TCM. The TCM uses inputs from the PCM to control the torque converter clutch operation. The TCM sends a pulse width modulated (PWM) signal to the TCC solenoid (located on the valve body). The TCC solenoid regulates the pressure going to the TCC regulator valve in the valve body.
The TCC regulator valve regulates apply & release pressure going to the torque converter clutch system through the stator support and on into the torque converter. A worn or faulty TCC solenoid, a worn TCC regulator valve, excessive bore wear in the valve body, worn stator bushings or a faulty torque converter can cause torque converter clutch concerns.
TORQUE CONVERTER CLUTCH SLIP DIAGNOSIS:
During torque converter clutch apply, the TCM modulates the TCC apply pressure in order to maintain a TCC slip of between 20-50 RPM, depending on driving conditions. Since we already checked for codes and no hard fault or memory codes returned, the next step would be to check the TCC duty cycle going to the TCC solenoid during TCC operation.
During the test drive, the TCC duty cycle was between 45 & 60 percent, which is within operating specifications. Next, we needed to check the transmission operating pressure. Low, high or erratic line pressure can interfere with torque converter clutch operation.
We installed our pressure gauge into the line pressure port (Figure 1) (left side of transmission, forward of shifter linkage), using an M10X1.00 t/p adapter and checked the line pressure. The transmission pressure was within specifications with 90 psi at an idle and rose to 230 psi at wide open throttle in drive and reverse.
The next step was to remove the transmission pan and inspect the fluid condition for any signs of debris (TCC debris). The transmission fluid was clean and there was no signs of debris in the pan. We removed the TCC solenoid (Figure 2) (located on the front of valve body) and checked the solenoid resistance. The TCC solenoid resistance was within specifications at 5.0 ohms. We check the TCC solenoid operation and it was operating properly.
Next, we removed the valve body assembly to inspect the TCC regulator valve and bore for wear (Figure 3). We performed a vacuum check on the TCC regulator valve train and found the TCC regulator valve and bore were leaking down below 10 inches of vacuum. This was an indication that the TCC regulator valve and bore were worn. With the transmission fluid being clean and no torque converter clutch material in the pan, we were certain we were looking at a TCC regulator valve & bore wear concern. It was time to repair or replace this valve body.
REPAIR OR REPLACE:
We contacted our local suppliers to check on availability of a valve body repair kit. Unfortunately, there were no valve bodies or remanufactured valve body repair kits available at this time. We contacted our local dealership and purchased a new valve body assembly. We flushed the transmission system prior to installing the new valve body and filled the transmission with Mercon ULV fluid. We reprogrammed the TCM with the latest calibration update and then headed out for our final test drive.
MONITORING THE TEST DRIVE:
After we replaced the valve body assembly and reprogrammed the TCM with the latest calibration update, it was time to head out for our final test drive. We connected our scanner to the DLC connector so we could monitor the torque converter clutch operation during the test drive. We drove the vehicle through city streets and on the highway. We drove through the local grocery store parking lot at 5-10 mph and the TCC slip remained between 20-50 RPM and there was no rumble sensation felt. The vehicle was driven several times with no further concerns, so we delivered it to the customer. We have contacted the customer several times and he says he no longer gets the rumble sensation while driving.
Well, there you have it, it looks like we fixed another one. With a better understanding of how the 10R80 torque converter clutch system operates, you should have no problem Keeping Those Trannys Rolling.