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Glossary List of Categories
- What does the term non-synchronous shifting mean?
- What does the term synchronous shifting mean?
- What is an EEC PCM?
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What does the term non-synchronous shifting mean?
A non-synchronous shift is one in which no timing (synchronizing) of holding elements is necessary because no clutch or band has to turn off while another clutch or band is turning on. For example in the AOD, AODE, or 4R70W the 1-2 and 2-3 shifts are non-synchronous. For first gear the forward clutch is engaged. When second gear comes in the forward clutch remains on and the intermediate clutch engages. When third gear comes on the forward and intermediate clutches remain on and the direct clutch engages. This type of shifting results in very quick shifts with excellent feel and very little clutch/band wear.
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What does the term synchronous shifting mean?
A synchronous shift is one in which timing (synchronizing) of holding elements is necessary because a clutch or band must turn on or off while another clutch or band turns off or on. For example in the AOD, AODE, or 4R70W the 3-4 shift is synchronous. When shifting from third to fourth the forward clutch must turn off while the Overdrive band turns on. This must happen at precisely the right time, and elements in the valve body work together to synchronize the two events to result in a smooth shift. If the forward clutch turns off before the OD band is applied you get a flare (Momentary neutral condition), but if the OD band turns on before the forward clutch turns off you get a bind during the shift (a big contributor to direct input shaft breakage on the AOD). Synchronous shift are much more complex than non-synchronous shift and are harder to get a good shift feel and often cause more wear to transmission components.
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What is an EEC PCM?
EEC stand for Electronic Engine Control. Ford uses different versions of this through the years. The most popular are EEC IV and EEC V. This primarily refers to the strategies or software version that the PCM (Powertrain Control Module) uses to determine how to run the engine. For example if I said I had an EEC IV PCM it would mean I had a Powertrain Control Module that used Electronic Engine Control version four software strategies.
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