Late, Hard Shift from 1 - 2. 5R44E

Hello, I've been coming to this forum to learn as much as I can about the 5R44E transmission in my 2002 Mazda B3000. I've learned a lot from reading about other people's problems, but now I'm having problems with my own transmission. It has late and hard jerking shifts from 1 - 2. If I am accelerating from a stop on level ground, the engine will go above 3000 rpm's before a sudden shift from 1 - 2 with a hard jolt. If I go very gently from a stop, the engine will shift at a much lower rpm but there is still a jerk going from 1 - 2. Shifts to all other gears are smooth. The car has about 215,000 miles and I've owned it since it was new. I did a fluid and filter change at 100,000 miles and 200,000 miles but nothing else to the transmission. Nothing unusual in the drained fluid or pan. No metal debris.

The ATSG manual for the 5R55E shows that the only thing different from first gear to second gear is that the front (overdrive band) is applied. All other bands and clutches are unchanged from first gear. I checked the overdrive band adjustment and it's OK. So, working back from the band, there is the servo piston, the shift valve that controls the pressure to the servo piston, and the shift solenoid that controls the shift valve. Is there anything else I should be looking at? Could the EPC solenoid cause the problem even though all other gears are fine?

The overdrive band is also applied for 5th gear but there are no problems shifting into that gear. It's very smooth and hardly noticeable. If the valve body gasket is blown, wouldn't it show up in problems with the 5th gear since the same band is applied?

I don't have a scanner that will read the codes but I may buy a Harbor Freight unit since I read it will display transmission codes.

Does anyone have any ideas? Should I also be looking at sensors? Thanks