Hey Scotty I have a 2007 Acura MDX and it lags when shifting from park to drive and reverse to drive but not park to reverse. There is also a vibration when in third gear lockup and the rpms struggle to stay constant and fluctuate. This doesn't happen on the highway is 5th gear lock up. The fluid is 100 miles old, all the other gear shifts are crisp, is this a torque converter problem or a transmission problem or both? TIA

transmission is starting to go out, typical on those. Most of my customers with that model already have paid for a transmission overhaul, and it's not cheap. You might consider dumping it now if you don't want to spend many thousands on that job