Auto transmission question
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Auto transmission question
Hi all. I'm new to the diesel super duty scene. Just bought a used 2003 F-350 and had a question. When I drive in"tow" mode I can hear the rpm drop from the torque converter. However, when tow mode is off and I'm in fourth (overdrive) I dont hear the rpms drop. Is this normal? Seems like other vehicles rpms drop at highway cruising speed. Is this normal? Thanks!
Frmr Ford Trans Engr
Joined: Aug 1999
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From: SE Florida
I assume that you have a 7.3L diesel, right? If so, there is no "tow" mode on that truck. There is a button on the end of the shifter that turns off the overdrive.
When you are in fourth gear (overdrive) the torque converter will lock up if you are over about 40 MPH. It usually will lock during the 3-4 shift, so you won't notice a separate RPM drop for the lockup.
You can check it at 45-50 MPH. Hold the go pedal so that you are at a constant speed for at least 10 seconds. Without moving the go pedal, use your left foot to gently press the brake pedal. When the brake pedal is pushed the torque converter will unlock and engine RPM should rise by about 200 RPM.
When you are in fourth gear (overdrive) the torque converter will lock up if you are over about 40 MPH. It usually will lock during the 3-4 shift, so you won't notice a separate RPM drop for the lockup.
You can check it at 45-50 MPH. Hold the go pedal so that you are at a constant speed for at least 10 seconds. Without moving the go pedal, use your left foot to gently press the brake pedal. When the brake pedal is pushed the torque converter will unlock and engine RPM should rise by about 200 RPM.
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