1999 Olds Intrigue with 165,000 miles

My car has is the 3.5L engine version and has 165,000 miles. I estimate that at least 90% of the miles have been highway, using cruise control whenever possible. I really like this car and want it to go another 100,000. within the past couple of months I’ve noticed that when accelerating from a stop the engine seems to rev harder than usual until the car shifts and the shift seems hard (vs. smooth) to me. this is less pronounced if I accelerate more slowly (which is not to say that I’m racing out of my stops). I have never had to do any transmission work on the car and want to know 1. if this is a sign transmission service is needed. 2. is there a trany service I should be considering at this milage. FYI I have always had the car serviced at the dealership where I purchased it and have always used hi test gas. (I used regular at the very beginning but like the way the car performed better on high test) I am, overall, happy with this car.

When you say that you have never done any transmission work does that mean you never had the fluid changed, pan dropped, and filter changed?

If so your transmission has probably lived its life and you need a new one.

Sorry to say J is likely right.  A fluid change or two before there is a problem, can go a long way towards extending the life of a transmission.  Every 30- 80 thousand miles would be my recommendation .

If you have always had the dealership perform your scheduled routine maintenance, that would include changing the transmission and fluid (about every 35,000 to 60,000 miles). Question your dealer.
"…the engine seems to rev harder…" Would you explain what you mean by that? Is the rpm shooting up, or does the engine sound louder and exerting more effort for the same amount on acceleration, or what?
You may need the services of a transmission shop if the rpm is going up, but, the car isn’t accelerating.

Sounds like transmission is slipping, fluid and filter change most likely not going to do much. However you may take car to a transmission shop for re-adjustment, but considering 165.000 miles you may need new transmission.