2001 Tacoma A44D transmission

I have a 2001 Tacoma base 2WD with A44D automatic transmission & approx 175k miles. When shifter is in “D”, I feel a really hard kick when shifting from 1st to 2nd gear, only. This only happens periodically, not every time. It shifts normal most of the time. I drive it for work every day & I’m typically on the interstate for a few hours. There’s no vibration at any speed. At first, it sounded like the rear end kicked me in the butt. There’s no pattern of when this will happen. I’ve tried to analyze it with gentle, medium, full acceleration from a full stop, straight forward or turning either direction. It doesn’t seem to matter how I accelerate or how long it’s been running. I’m thinking about swapping the trans fluid to a full synthetic with fluid flush.

I have 2 questions: 1) What could be causing this hard shift? 2) Do you have any thoughts on full synthetic trans fluid?

Thanks in advance for any suggestions, comments, thoughts, &/or solutions!

 

Did you find out what was the problem for your shifting concern? I have the same problem but it’s all the time. Other than that trunk runs great . My problem happen right after I was making a U turn and just jump on the gas pedal really hard and BANG harsh upshift 1st to 2nd . Now happens all the time now