OK, I just want to thank the OP for the most fun evening commute I've had in a while. I read this post, and I have I have a 2011 2.7 4 cyl 5 speed, with the 4.10 rear end because it's a 4x4, same as the OP. So naturally I had to "stretch" out the engine and tranny a bit, which is something I don't usually do in the interest of saving gas.
I drive about 20 miles of stop-and-go every morning and evening on the way to work. This evening, I paid a little more attention to my shifting and downshifting technique.
I shift effortlessly from 2nd down to first at about 8mph without thinking about it. That's just my basic stop and go heavy traffic downshift point, though I had to look at the speedo and tach to see what it was for purposes of this post. Typically I shift by ear. For fun I did an easy 15mph downshift from 2nd to first, and then a little later, just for giggles, I did a 25mph downshift from 2nd to first. Later in the commute, merging from one highway to the other, I downshifted from 4th to 2nd - that's actually a pretty common need in these little trucks, as is the 5th to 3rd freeway passing downshift. So the truck can do what you want.
The thing is, many (most?) folks who learn stick never learn good downshifting technique -- it's not something your driving school teacher really covers.
The first rule is anticipation. A proper downshift is while you're still decelerating, in anticipation of the acceration to follow. For example, downshift into a curve, before the apex, so you can accelerate out of it.
The second rule is throttle control. Your "garden variety" downshift is done the same as upshift - ease (or release!
) throttle, clutch, shift. This pushes the synchronizers in the transmission very hard, and beyond a certain speed difference, they simply can't force the gears to catch up to the engine speed. This is what OP is experiencing, and it always bugs me when I'm riding with someone who shifts this way.
Instead, the proper downshift is brake, clutch, throttle blip, clutch.
The throttle needs to cause the engine to gain between 1000 and 2000 rpms, depending on the gear. For the tacoma, the 3rd/2nd downshift is closer to 1000 rpm, and the 2nd first downshift is closer to 2000 rpm. Since you're decelerating, a good throttle blip will go a little *higher* than the desired RPM (but only by 100-200 rpm) so you can ease the throttle through the clutch release. (You're downshifting while still decelerating, remember?)
So back to those shift points - the 15mph shift starts at about 1500 rpm, blip to around 3500, and ease while releasing the clutch.
Similarly, the 25 mph 2nd to 1st downshift starts at a little above 2500 rpm. Clutch, throttle blip past 4500 - say 4800, and quickly ease the clutch back out as you're easing the gas to match the engine speed and further ease into engine braking.
Advanced technique is to brake with the lower left part of the right foot while blipping the throttle with the upper right part of the same foot. (this is the so called "heel and toe" braking.)
Synchros are your friends. Without them, you can *try* to jam into any gear at *any* speed and the transmission will not prevent you. But the resulting gear gnash surely will, unless you've carefully matched engine speeds. My 74 alfa romeo had a burnt 2nd gear synchro - that was common in those models - so I always double clutched the 3rd/2nd downshift. But there's no need to double clutch a Tacoma - just use the throttle. That 2.7 is willing, and will happily do what you want.
Disclaimer: following the advice in this post may lead to increased driving joy and decreased gas mileage. objects in the mirror are closer than they appear. beware of unmarked obstacles and sudden blinding dust storms. stove burners may be hot enough to burn.