Shaking at 2k RPMS 25mph 2005 V6 4runner in D

Hey all. I'm not a car guy, but I'm trying to become more knowledgable. I have an 05 4runner that has been my beater car since highschool (7 years). I lent it to my uncle for 2 years and now whenever I put it into D, the car shakes violently when accelerating in the 20's. I figured its a transmission issue, since the car doesn't shake at all in 4. Any advice would be greatly appreciated.

 

How many miles are on it? When was the last time the transmission fluid has been changed? I was going to suggest greasing your U-joint zerk fittings but since you said it doesn't shake in "4" that's probably not it.

 

Doesn't make too much sense with it in D and 4 if it shakes in the 20mph range while accelerating.

Doubt you are in anything besides 2 or 3 at that speed.

Can you drop it lower in the 4th Gen? And see if it does it in lower gears.