I have a '94 Toyota pickup, 2WD, Xtra cab, manual transmission, 22RE engine and about 142k miles on the clock. I’ve driven manual transmissions since I was 12 (I’m 42 now), and I have a habit of shifting pretty quickly. In the last couple of years, when using my normal shifting style, I often wind up grinding the gears, especially shifting from 2nd to 3rd. If I slow down my shift, perhaps pushing the clutch pedal a little further that usual, I can shift smoothly.
Potentially distracting evidence: Shortly after buying the truck new, I tried shifting without using the clutch (a valuable skill if you ever drive old VWs 
and noticed that it was quite difficult to get a speed match that allowed me to shift into 3rd without gear clash.
So what’s causing my gear clash with my normal shifting style? Clutch plate wear (clutch has never been replaced)? Syncro wearing out? My old brain wearing out?
[i] f I slow down my shift, perhaps [b] pushing the clutch pedal a little further that usual[/b], I can shift smoothly. [/i]
You should push the clutch in ALL the way every time you shift.
[i] So what's causing my gear clash with my normal shifting style?[/i]
It's your normal shifting style. It may or may not have worn the synchs. Take it to a good local independent mechanic have it checked and repaired and change your shifting style. BTW I have about 15 years of manual experience than you.I’ll defer to your experience and agree that I should change my normal shifting style. I’m going to disagree that I should take it to a mechanic and get it fixed (unless it gets to the point where it needs fixing to be drivable).
Hey, the thing has over 140k pickup truck, back road miles on it; not those easy, greasy highway miles. Most of the plastic parts are broken and most of the parts are plastic The KBB trade-in value, if I’m dishonest about its condition, is not much better than around 2500 bucks. I’d like to see it reach 200k miles, so I’d like to know what kind of impending doom, if any, that the apparently increased tendency to gear clash might portend.
Your truck may have some wear in the synchronizers. Your truck is getting older. Shift it more slowly between 2nd and 3rd. You might even double clutch shifting between these gears.
One other thought: be certain that your transmission isn’t low on grease.
I’ve had old cars where I had to shift slowly between gears due to worn synchronizers. I made them last. My first car, a 1947 Pontiac,had a worn cluster gear when I bought it. It sounded terrible when I would start off in first gear. I would start off gently and shift to second as soon as possible–usuallly about 5 mph. I’ve found out over the years that there can be a lot of worn parts in a car, but if you drive the car gently, it will still go for miles.
You need a special tool to see the problem, hanging in your bathroom.