Mitsubishi Repair: Gear not catching, montero sport, askia

Question
I have a 99 Montero sport 2 wheel drive automatic. I have no power when trying to accelerate down the road. When trying to accelerate, my rpm's are at 5000 not shifting or gaining anymore speed without increasing more rpms. I'll be doing 60 mph at a constant 5000+ rpm's. But after about 15 to 20 mins of driving that way, it would then finnaly kick into 2nd or 3rd gear automatically. Is this my transmission or do I need a tune up /or trans flush?

Answer
Askia: Before you do kill off your transmission get the car in someplace and get that fluid as well as the filter changed. While having that done, make sure the shop cleans the pan good, gets the old gasket off and puts the new one on good. But also as they clean the pan, ask to see what was in it. It will tell you a lot. If there is a lot of steel in the bottom. I would start going easy on my car because other wise you will be replacing or rebuilding your transmission soon. I am hoping the new fluid and filter will help it, anyway. Hope this helps and good luck!