car is missing going uphill. need tune up? on 1995 Ford Thunderbird

It has problem shifting into gears. Transmission?

Asked by for the 1995 Ford Thunderbird
It could be many things, unfortunately and without experiencing the problem first hand or being able to do some basic diagnostic tests its hard to say. Check the fluid level and condition, service the transmission if required and catch up engine tune up or maintenance required.
Thanx Patrick: All fluids were checked and normal. Had diagnostic check last year. How often should I get a tune up?