1/14/2024 0 Comments 6l90 torque converter![]() If the throttle is light and gradual enough, full lock up can be achieved before reaching 20 mph! CAUSE FOR ISSUEĪfter verifying that the issue was directly related to the TCC engagement, we still needed to find a solution to our problem. On light to moderate throttle, the torque converter clutch is modulated on as soon as second gear, based on engine demand. The TCC is fully commanded off, and the fuel injectors are commanded to operate before the vehicle comes to a complete stop. While coasting, the powertrain control programming turns off the fuel injectors and modulates the torque converter clutch to keep the engine at a low, steady rpm. More specifically, the coast down, low-speed torque converter clutch scheduling was modified. The powertrain management strategy for V8 applications model years 2007 through 2014 was modified to enhance fuel mileage. With no check engine light or faults to point towards, we had to figure out what could be causing this issue outside of the box. The truck was unacceptable to deliver to the customer. ![]() As suspected, we observed that the torque converter slip speed was very low, and the PCM was commanding it. ![]() It was also present on the coast down from 20 mph to almost stopped, but not as noticeable.Ī scanner was connected, and we watched the torque converter clutch command and slip parameters to see exactly what was going on during our shuddering condition. Further testing showed the shudder sensation was present at light throttle (low RPM from 10 to 20 mph). While going through the final check procedures, the diagnostician noticed a shudder while coming to a stop. The customer agreed to the repairs, and the job was completed quickly. The vehicle was well maintained, clean, and drove well (with the exception of a tired transmission). A simple test drive and a scan showed us quickly there were no driveability concerns on the engine side that may need to be addressed along with a transmission repair. We had a typical 2008 Chevy Tahoe with a 4L60E transmission come into a shop slipping in 3rd and 4th gears. Let’s look at a 4L60E that falls into this category. Engine misfires, cylinder balance, torque converter integrity, and powertrain isolation become possible sources for complaints. ![]() With all possible strategies taken into consideration, things can become unpredictable when these vehicles begin to age. In most late model applications, lock up is even commanded on during coast down. Now, lock-up is commanded as often as possible. In the past, lock-up was assigned exclusively once the vehicle reached high gear with medium to light throttle. One major area that has helped automakers create more efficiency in powertrain management is lockup control. After all, we live in an imperfect world! With a micromanagement level of control in play comes an opportunity for things to go wrong. ![]() Powertrain management computers control the engine, transmission, and related systems to prevent wasting fuel. Every component is designed to maximize the transfer of power with the minimum amount of waste while maximizing the driver’s comfort and overall experience. Today’s drivetrains are more efficient than ever before. ![]()
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