Auto NA FC Question
03-30-06, 07:47 PM
#1
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Auto NA FC Question
1991 Mazda rx-7 red 106,000 miles 2 owners automatic only $1500.
Runs great it has a new transmission and a new torque converter...it has a problem with shifting...it wont shift under a load you have to let off the gas for it to shift...i think it is a sensor or solinoid or something ....but anyway here are some pics.
This is what was posted on another car forum I'm on. I was wondering if anyone had any ideas as to why the car would not shift without letting off of the throttle.
Runs great it has a new transmission and a new torque converter...it has a problem with shifting...it wont shift under a load you have to let off the gas for it to shift...i think it is a sensor or solinoid or something ....but anyway here are some pics.
This is what was posted on another car forum I'm on. I was wondering if anyone had any ideas as to why the car would not shift without letting off of the throttle.
03-30-06, 09:07 PM
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I'm not seeing any pictures, but check and see if the vacuum tube from the engine is hooked up to the transmission. There is only one vaccum tube that goes down to the trans and it needs to be hooked up or it won't shift properly.
03-30-06, 10:20 PM
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Make sure the fluid level is full (but not over full). Improper fluid level is the most common cause of auto transmission problems and can lead to internal damage.
I've seen the same problem you discribed on other cars, most recently my friends BMW. All auto transmissions need something to tell it how much work the engine is doing and this is done by vacuum hose or by mechanical cable attached to the throttle plate linkage. It also measures rear wheel speed by a pressure device in the transmission tail output shaft. The two "signals" so to speak, are compared in the vacuum modulator. If you floor the gas, the tranny will shift later because it will take a longer period of time for the rear wheel pressure monitor to over-come the pressure input from engine. If the vacuum hose is not attached and working properly, the vacuum input signal will show no vacuum which is atmospheric pressure (which occurs at wide open throttle) and the rear wheel pressure will have to build to a higher point before the tranny will shift. This will cause the car to stay in 1st gear, shifting very late, or not at all. My friends BMW had a cable connection and the cable was pulled out of its housing and would not retract, thus it was holding the tranny lever to the wide open throttle position. Same thing, 50 MPH in 1st before it finally shifted.
(Tranny operation discription was somewhat generalized. More info can be found at www.howstuffworks.com )
I've seen the same problem you discribed on other cars, most recently my friends BMW. All auto transmissions need something to tell it how much work the engine is doing and this is done by vacuum hose or by mechanical cable attached to the throttle plate linkage. It also measures rear wheel speed by a pressure device in the transmission tail output shaft. The two "signals" so to speak, are compared in the vacuum modulator. If you floor the gas, the tranny will shift later because it will take a longer period of time for the rear wheel pressure monitor to over-come the pressure input from engine. If the vacuum hose is not attached and working properly, the vacuum input signal will show no vacuum which is atmospheric pressure (which occurs at wide open throttle) and the rear wheel pressure will have to build to a higher point before the tranny will shift. This will cause the car to stay in 1st gear, shifting very late, or not at all. My friends BMW had a cable connection and the cable was pulled out of its housing and would not retract, thus it was holding the tranny lever to the wide open throttle position. Same thing, 50 MPH in 1st before it finally shifted.
(Tranny operation discription was somewhat generalized. More info can be found at www.howstuffworks.com )
Last edited by Project84; 03-30-06 at 10:25 PM.
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