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Torque converter

17 April 2005
Wellington, FL
do the 95 &up automatics with the manual shifter on the steering wheel release the torque converter when it shifts or does it do the same thing as if you were to shift from 1 to 2nd to 3rd to drive on a regular autmatic.
Actually, the torque converter does not lock and unlock during shifting. This is a popular misconception. (Except for the VW Type I AutoStick) In an auto, parts never move the way they do in a manual. Inside the trans, each gear has its own clutch(pak) Hydraulic pressure is routed by the computer, solenoid valves, and a valve body to each clutch pack and when a gear is selected, that pressure engages that gear by slamming the clutches in the pak together. When gears change, one pak bleeds pressure while the next pressurizes so only one gear at a time is engaged. The differance between computer shifting and you shifting is merely a matter of who sends the shift signal.
Reverse is the exception- it has a small hub and slider identical to the manual trans operated by a piston and servo in responce to the computer signals as the other gears.

Torque converters use a turbine / pump assembly to make enough fluid pressure to drive the car as "if" mechanically linked. At idle, low engine speed drops pressure in the pump allowing the car to idle without stalling becuase the hydraulic "link" is weak. I could explain this much more technically, but would probabally put you to sleep.

The exception to this fluid drive is the "lock up" feature which sends a signal to the tourque converter to engage a part which does mechanically link the drive shell 'halves'. This occurs when the computer 'sees' fourth gear, road speed over 40, and map sensor voltage low enough to know that you are cruising. This is a fuel economy (and therefore emmissions) feature which is based on the fact that a fluid drive is not quite as efficient a direct one.