On my way back from school today when I was getting on the freeway I noticed my tranny seemed really weird. I was in second getting on and I barely pressed the gas and my revs shot up to about 4500 like i was in neutral but I made sure I was in drive. This happened the whole way back home when I went to pass someone revs would shoot up and take 3-5 seconds to engage the gear and the gear still didnt feel firm. So I took it on a long road and floored it and it shifted perfectly with the power getting to the wheels with no problem. So its just at cruising speeds it has trouble shifting. Any ideas? and the tranny was rebuilt a little over a year ago and fluid is in safe levels.