Automatic Transmission History
ChangingTransmission Fluid
How Transmissions are made.
Planetary Gear Theory
The heart of the Automatic transmission is the Torque Converter. It acts just like a clutch system but uses hydraulic pressure to make it work. Here are the Main parts of the torque converter.
1. Impellor (or pump)
2. Turbine - Connected to the input shaft
3. Stator - Creates the torque until the coupling stage
4. One way clutch - part of the stator
5. Lock-up clutch - Eliminates the 10% slippage factor
6. Torque Converter hub - Connects to the oil pump
Shift Terms
Firm - A noticeable quick apply of a clutch or band that is considered normal with a medium to heavy throttle shift. Should not be confused with "harsh" or "rough".
Flare- A quick increase of engine rpm accompanied with a momentary loss of torque. This mostly occurs during a shift. Also defined as slipping.
Harsh ("rough") - a more noticeable apply of a clutch or a band as compared to "Firm". This condition is undesirable during any throttle position.
Hunting - a repeating quick series of upshifts and downshifts that causes a noticeable change in engine rpm. An example could be described as 4-3-4 shift pattern. Also defined as busyness.
Initial feel - a distinct firmer feel at the start of shift as compared to the finish of a shift.
Late - a shift that occurs when the engine is at a higher than normal rpm for a given amount of throttle.
Shudder - a repeating jerking sensation similar to ,A chuggle" but more severe and rapid in nature. This condition can be most noticeable during certain ranges of vehicle speed. May also be used to define the condition after converter clutch engagement.
Slipping - a noticeable increase in engine rpm without a vehicle speed increase. A slip usually occurs during or after initial clutch or band engagement.
Soft- a slow, almost unnoticeable clutch apply with very little shift feel.
Surge - a repeating related feeling of acceleration and deceleration that is less intense than a 'chuggle'.
Tie-up - a condition where two apposing clutches are attempting to apply at the same time causing the engine to labor with a noticeable loss of engine rpm.
Noise conditions
Chain noise - a whine or growl that increases and fades with vehicle speed and is most noticeable under light throttle acceleration. May also be noticeable in PARK or NEUTRAL operating ranges with the vehicle stationary.
Final drive noise - a hum related to vehicle speed and is most noticeable under light throttle acceleration.
Gear noise - a whine most noticeable in first gear or reverse that is related to vehicle speed. A gear noise condition may become less noticeable or go away after an upshift.
Pump Noise - a high pitch whine that increases in intensity with engine rpm. This condition may also be noticeable in PARK and NEUTRAL operating ranges with the vehicle stationary.
Throttle Positions
Minimum Throttle - The least amount of throttle opening required for an upshift.
Light Throttle - approxamately 1/4 of accelerator pedal travel.
Medium Throttle - Approximately 1/2 of accelerator pedal travel.
Heavy throttle - Approximately 3/4 of accelerator pedal travel.
Wide Open Throttle - Full travel of the accelerator pedal.
Full throttle detent downshift - a quick apply of the accelerator pedal to it's full travel, forcing a downshift.
Zero throttle coastdown - A full release of the accelerator pedal while the vehicle is in motion and in drive range.
Engine braking - A condition where the engine is used to slow the vehicle by manually downshifting during a zero throttle coastdown.
Shift Conditions
Bump - A sudden and forcefull apply of a clutch or band.
Chuggle - a bucking or jerking condition that may be engine related. May be most noticeable when the converter clutch is engaged. Similar to the feeling of towing a trailer.
Delayed - a condition where a shift is expected but does not occur for a period of time. Samples of this condition could be described as a clutch or band engagement that does not occur as quickly as expected during a part throttle or wide open throttle apply of the accelerator or, when manually downshifting to a lower range.Also defined as 'Late" or @Extended:".
Double bump - ("Double feel") - two sudden or forcefull applies of a clutch or a band.
Early - A condition where a shift occurs before the vehicle has reaches a proper speed and tends to labor the engine after the upshift.
End Bump - a firmer feel at the end of a shift as compared to the feel at the start of the shift. Also defined as 'End Feel' or, 'Slip Bump'.
Preliminary Checking Procedure
* Fluid Level high / low
* Engine performance
* T.V. cable adjustment
* Manual linkage adjustment
* External fluid leaks
* Electrical system
* Transaxle or other mechanical component
* Vacuum modulator
Noise and vibration analysis
A noise or vibration that is noticeable when the vehicle is in motion. MAY NOT be the result of the transaxle.
If the noise or vibration is noticeable in 'Park'(P) and in neutral(N) with the engine at idle, but is less noticeable as RPM's increase, the cause may be from poor engine performance.
INSPECT:
Tires for:
- Uneven wear
- Imbalance
- Mixed sizes
- Mixed radial and bias ply
Check suspension components for:
- Alignment and wear
- Loose fasteners
Check engine and transaxle mounts for:
- Damage
- Loose bolts
Transaxle case mounting holes for:
- Missing bolts, nuts and studs
- Stripped threads
- Cracks
Flexplate for:
- Missing or loose bolts
- Cracks
- Imbalance
Torque Converter for:
- Missing or loose bolts or lugs
- Missing or loose balance weights
- Imbalance
