Automatic Transmission Basics
Hydraulics, solenoids, adaptions and how a jerking complaint is actually diagnosed.
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What you will learn
- Describe how an automatic shifts
- Explain adaptions
- Plan a jerking/slip diagnosis
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A conventional automatic transmission uses fluid pressure, controlled by valve body solenoids, to engage clutches and brakes inside the gearbox. The transmission control unit decides shift points from throttle, speed and load, and commands the solenoids accordingly.
Adaptions are learned corrections that let the box compensate for clutch wear over time. Diagnosis of a jerking complaint starts with fluid level and condition, then codes, adaption values and shaft speed sensors — not with a rebuild.
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Key points
- Fluid quality and level are non-negotiable.
- Solenoid or sensor faults can mimic internal wear.
- Perform a relearn where the manufacturer allows before condemning the unit.
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Key points
- Fluid pressure does the shifting
- Solenoids are controlled electrically
- Adaptions let the box compensate for wear
All values shown are training examples. Real thresholds depend on the manufacturer, engine, temperature and system — always confirm with the vehicle service documentation.
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