What is my tranny doing?
In an attempt to conserve gas I have been experimenting with taking my foot off of the gas pedal during the longer downhill portions of my commute to work that don't have an immediate uphill climb after them. At 55 mph my RPMs are around 2000. When I take my foot off, they drop to 1500 or so. However, after maybe 10 seconds (if I get a glide that long), it will do what seems like an upshift and the RPMs will drop to just above 1000. If I glide in anything other than overdrive, it will drop to 1000 first. It's only when I'm in overdrive and glide that it does these increments.
However, no matter if I begin accelerating again with the RPMs still at 1500 or after they've dropped to 1000, I'll start in 4th gear. Obviously I'd like it to be in overdrive right away. I'm not dropping speed that much. If i just loosen the gas pedal a little so that I just slow down the tranny won't downshift into 4th until 45 mph. But on these downhill glides I normally put my foot back on the accelerator at around 50 mph, and when I do it feels like it's shifting into gear from neutral or like a regular upshift.
I've heard on here that my tranny isn't shifting into neutral during these glides (maybe just the torque converter being locked/unlocked), but why the two different "stages" of RPMs? Am I really saving any fuel doing this? I normally have to have my foot on the gas for 2-3 seconds, even if I don't accelerate at all, in 4th gear before it'll shift into overdrive again. Would my injectors not be flowing any fuel at the 1500 RPM stage, or the 1000 RPM stage?
The tranny isn't broken, it performs flawlessly. I was just curious about these quirks and how they affect my FE.