AUTOMOBILE TRANSMISSION PROPERTIES

The kind of transmission you have can determine what you can do with it. Here is a table showing what each type can and cannot do:   Difficulty scale:  EASY  ......  ......  HARD

TYPE	MANUAL	AUTOMATIC
PROPERTY	MANUAL CLUTCH AND SHIFT	HYDRAULIC COUPLING	SIMPLE TORQUE CONVERTER	MULTIPLE TURBINE CONVERTER	CONTINUOUSLY VARIABLE
Diagrams P = Planetary gearset R = Reverse planetary set
Examples	Synchromesh All makes	Hydra-Matic 1950s	Most Automatics Most makes	Dynaflow, Turboglide GM 1950s early 1960s	Nissan, Toyota, Volvo, Mostly foreign makes
Concept	Manual plate clutch Manually shifted gears	Hydraulic coupling Planetary gears change	Single turbine Planetary gears change	A turbine for each gear Planetaries set ratios	Variable size pulleys Drive belt
How gears change	Synchronizing plates engage each gear	Each planetary is set to reduction or direct	Planetary sets provide many gear ratios	One-way clutches pick which turbines drive	Pulleys change size to choose gear ratio
Shift smoothness	Depends on driver skill operating the clutch	Early models rough Audible thumps	Modern units smooth Jerks on heavy load	Can't detect shifts between turbines	Shifts noticed as engine pitch changes
Drive gear choice	Driver chooses gear with gearshift	Shift control logic and sensor data pick gear	Shift control logic and sensor data pick gear	One-way clutches pick which turbines drive	Shift control logic and sensor data pick ratio
Coast gear choice	Driver chooses gear with gearshift	Shift control logic and sensor data pick gear	Shift control logic and sensor data pick gear	Always in highest gear when not loaded	Shift control logic and sensor data pick ratio
Engine brake gear	Driver chooses gear with gearshift	Driver selects gear range with gearshift	Driver selects gear range with gearshift	Driver selects retarder range with gearshift	Driver closes throttle
					(some have low range)
Special winter gear	Driver chooses gear and slips clutch	Driver selects D2 range	Use second gear start*	Driver selects retarder range with gearshift	No provision for winter driving
		(Not often provided)	(Usually not provided)
Climb steep hills	Driver picks one gear for both bottom and top	Driver selects L range for more torque	No action necessary Automatically done	No action necessary Automatically done	No action necessary Automatically done
Mountain descend	Driver downshifts with gearshift	Driver selects low gear range with gearshift	Driver selects low gear range with gearshift	Driver selects retarder range with gearshift	No provision for this
					(some have low range)
Sharp curves	Driver picks one gear for the situation	A shift might cause a loss of traction	A shift might cause a loss of traction	No abrupt shifts to disrupt traction	No abrupt shifts to disrupt traction

* This feature is available on only some makes, models, and years of cars.

1. Some GM cars made in the 1990s have a Second Gear Start switch.
2. Many European cars have a winter driving switch that omits first gear.
3. Some versions of the original HydraMatic transmission have a D2 position that omits first gear.
4. Most 3 and 4 speed transmissions made by Ford, Honda, and Kia have a 2 position that gives only second gear. The driver must shift to Drive at higher speeds.

   - Note that other makes with 2 positions do not omit first gear.

5. Chrysler products with the dual-gate shifter can start in second gear.
6. Manumatic transmissions made by Kia, Mazda, and Hyundai can be made to stay in second gear.
7. Most of the 2-speed automatics (Powerglide, Jetaway, Powerflite) give the same needed ratio in Low.

LINKS

• More on a winter driving position
• Add a winter driving control to a post-1994 GM car with 4-speed automatic
• Unusual traffic problems
• Home page