Transmission issue?

Hey guys. I bought a used 2009 Toyota Tacoma trd sport doublecab about two weeks ago with around 120,000 km. I love the truck but when I accelerate slowly (around 20-25km) I'll feel a jump/jerk with the vehicle. It's nothing crazy but definitely noticeable. I'll notice it more when I'm in bumper to bumper traffic and stopping/starting much more often. Once I'm driving 30 km and over and accelerating faster there is no issue. Any idea what this might be? I took it to a mechanic and he said he didn't find anything wrong.

Thanks,
Cory

 

Did the mechanic drive it and experience the thud?

Does the thid appear to happen during a shift point?

At 120k miles on a used truck I don't know the history of I would be planning on taking it to a good mechanic/trans shop and having them drop the pan, inspect everythin and do a full fluid flush anyways. This is even more reason to do it.