46RE ticks in all gears except reverse

Throttle pressure related was what I was thinking as well, but I didn't consider it until I'd tugged on the TP cable. I'm also wondering about any "thrust force" that's applied inside the trans when it's in reverse. I had the truck pretty well warmed up by then, as I was running the heater to make sure the interior was nice and dry. Ambient temperature didn't change (about 50 all day), and I also pushed the TP lever all the way forward later with no change. There's good engagement in all gears, but reverse has the notorious valve body whine (that seems to be common with these transmissions) barely audible when moving much over an idle. I'm gonna go out and fire it up again, see if the TP lever makes any difference when the truck is cold.