GM Transmission Troubleshootingby Wesley Tucker
GM transmissions, both standard and automatic, come in several variations. GM transmissions have different numbers of gears, gear sizes and specification depending on the vehicle and performance requirements. A transmission for a small Chevy Cobalt is not the same found in a Cadillac Escalade. Whichever transmission is in your GM vehicle, there are common components making finding and troubleshooting problems similar. When the transmission starts to fail, the first step to correcting the problem is finding the transmission part or parts no longer functioning properly.
Slow or no Gear Change
If you accelerate your GM vehicle and the engine revs very high before changing to a lower gear you could need more transmission fluid. Another problem with automatic transmissions is the integrated control (computer) is not functioning properly. It controls when and under what conditions to change gears in some GM vehicles (Tundra, Yukon, Corvette, Buick Lucerne). Any problem related to the transmission could possibly be attributed to low transmission fluid. Standard transmissions (gear changed by foot pedal and gear shift) also have transmission fluid sealed in the transmission case. Adding fluid or completely draining the old fluid for a fresh refill can fix some gear-change problems. When changing transmission fluid also check the transmission fluid filter. If it is full of debris and clogged it will interfere with transmission fluid flow.
Burning Smell and Noises
Several bearings are seated in the transmission. When a bearing goes it most often will grind, create friction and make an acrid smell. Fortunately, transmission fluid is not flammable, but the bad bearing will affect transmission performance. Bearings also may chatter or make grinding noises when they start to go bad. Noises like a small bell ringing ("tink-tink") may indicate the torque converter is the source of the problem. The torque converter is needed to control the power from the automatic transmission to the drive shaft. It’s easy to misdiagnose torque converter malfunctions as a transmission problem.
If the clutch in a standard transmission GM truck, Corvette or Camaro begins to feel loose and there are noises with the clutch pedal pushed in the pressure plate is failing. You can drive as the plate wears but eventually it will no longer adhere to the clutch plate and the car will not run. The only repair for this problem is a clutch replacement.
Can't Shift Automatic Tranmission
If the shift lever or console knob will not shift into drive or reverse, it indicates a bad first or reverse gear. The only repair option is a complete transmission rebuild.
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