Whats your tire size? Stock or oversized?
For me, i have 33's, and i always put it in 3rd.
Theres been a couple times i put it in D and didnt notice, and the engine would bog down at about 40-45 when it shifted into overdrive, when it shouldnt shift until like 60.
Even on the highway, i just leave it in 3rd. Fastest ive been is 80-85 and i really should be in overdrive, but it was only for a couple seconds and the engine was at like 3600 rpm so nothing too crazy IMO.
But, what everyone tells me to do is when i get going about 60-65 let off the gas, and shift it up 1 gear into D, and ive done it and it keeps the engine at a nice low RPM, but i hate doing it because ive hit neutral before instead and had to get back down to D while on the higway, little sketchy for me.
If you have stock tires, just go D.
And, try both. Go 0-60 or so in D, see if at some point it bogs down on your or sounds wierd, if it does that go with 3rd.