Our van, with 103,000 miles on the clock, has presented us with a new challenge, and that is delayed shifting. Here's what it's doing: it shifts fine, up until the final shift into Overdrive. At that point, it does not want to make that final shift. At that point, the van is approaching 45-50 MPH, and, in my opinion (no tach), the engine RPMs are excessively high. But it still won't make that final shift into Overdrive.
The van does the same thing when I turn the Overdrive function off by depressing the button. The van does not want to make that final upshift.
The 46RE transmission fluid is clean, not burned, and at the correct level. The transmission fluid and filter were both changed about 15,000 miles ago. The PCM is not throwing any codes.
The puzzling thing is that it does not do this all the time. Sometimes it shifts flawlessly up and down the entire shift cycle. I've had the van at our mechanic twice (first to have the fuel pump replaced, and later to have the Onan generator repaired) and twice he took it for a test drive with me. Of course it shifted flawlessly during both test drives.
But I've found a way to "force" the final shift
: If I take my foot off the gas pedal for a moment the transmission makes the final shift into Overdrive, or makes the final upshift if I have the Overdrive function turned off. No idea why this happens, but when I take my foot off the gas pedal, the engine RPMs drop, and the transmission makes that final upshift.
I don't think it's related, but the orange shift indicator (on the steering column) has never read right. The reason I don't think it's related is that the delayed shifting is a recent issue, and the orange shift indicator has been "off" from the day we bought the van. "Park" reads way to the left of the "P", "Reverse" is between the "P" and the "R". "Neutral" reads between the "R" and the "N". And "Drive" is between the "N" and the "D".
My son, a supervisor at a car repair facility, said it sounded to him like a dead spot on the Throttle Position Sensor (TPS
). He thinks the TPS
is sending incorrect signals to the PCM, which, in turn, is sending incorrect signals to the electronically-controlled transmission.
But my son has not looked at our van. He's in Tennessee, and I'm in Texas, and I don't want to throw parts at the problem. Does a faulty TPS
sound like a logical cause of our van's delayed shifting?