car doesn't speed well especially when i use the ac

Thank you so much for you response, the car seems to move freely when the ac is off but as soon as i turn it on, the acceleration almost immediately drops, it struggles to reach top speed. it doesnt give good bursts of speed when i push down the tottle/accelerator . its a v6, it used to be a joy to push down the tottle and hear it "roar" and take off, i dont get that anymore. i tend not to use my air conditioner, only if its extremely hot. I have also noticed it wont go passed 100kph. bottom line, it now drives like a 4cl engine. the gear selects reasonably well bt sometimes its not as smooth wen shifting. i love the car but looks like i might have to sell..

Thanks for your response. What are the symptoms of a defective transmission?

Could be transmission fluid level or filter partially clogged if that's not it could also be alternatorbeen check output on alternator just because of runs worse with a/c on let me know if I helped you