2008 pathfinder bucking at highway speeds

[tanner94]

I have a 2008 nissan pathfiner 4.0 auto.
It has a trans cooler bypas.
today i did a trans fluid change just drained the pan not a flush i used matic j drained out 3.5litres added 3.5 litres the oil that came out was dark and had a slight purple ting almost some kind of pink.
So after i do this i leave work hit the highway right away about 10miles all the sudden it makes like a thump/ bang kind of like hitting a pot hole at a good speed (im doing 70mph btw) noise and feel is similar to revving engine a little bit in neutral and slamming it in drive it happened 3 times each time was about 20 miles in between