What makes tranny to shift??
Thread Starter
Junior Member
Joined: Oct 2004
Posts: 30
Likes: 0
E240 2004
What makes tranny to shift??
Would somebody tell me how does transmission up shifts. Please don't refer me bowden cable. Ok lets work out this way with an example;
Assume a car is standing still on top of a mountain, and you start moving it downhill without throttle but engaging the transmission (in D). You are not touching the throttle but car is accelerating (because of gravity) and upshifting. Now what is causing it to upshift???
Assume a car is standing still on top of a mountain, and you start moving it downhill without throttle but engaging the transmission (in D). You are not touching the throttle but car is accelerating (because of gravity) and upshifting. Now what is causing it to upshift???
Senior Member
Joined: Aug 2004
Posts: 285
Likes: 0
From: Richmond, Va.
1991 300E
The transmission senses the vacum that is created by the engine running at higher RPM. In your mountain example, even though you are not pressing the accel., gravity is causing the car to move faster. This in turn makes the engine turn faster and creates more vacum and causes the transmission to shift up. It is possible (though not recommended) to adjust the rpm(vacum) that your car will up shift/downshift at.
