Alternator changed now transmission not working well. Any connections? on 2004 Mazda B2300

I changed out the alternator then shortly after the 2nd gear in the transmission became sluggish. Now I have to let off the accelator to get it to shift into second gear. Any ideas.

Asked by for the 2004 Mazda B2300
I dont think that would any connections. Sound like one of the shift solenoid sticking and needs to be replaced. Did you have transmission fluid changed recently? If not that would be good to do both things together.
Any idea how much this type of repair might cost
The whole thing should cost under 300$.