05 elantra.I dont know what the problem is, help? on 2005 Hyundai Elantra

I have a 2005 hyundai elantra, 108k miles on it and when I drive at constant throttle and imbetween around 30mph - 40mph my tachometer bounces up and down a bit, sometimes more. It seems to lose power sometimes to and the engine does rev in connection to the bouncing of the tach. Also sometimes when slowing down and I slow to about 20mph I get a jerk as if it went to too low of gear. I have rplaced TPS and the input speed sensor, do I need the output as well? Or is it even a speed sensor? Does anyone have an idea on this? There is no check engine light on.

by in Lowellville, OH on October 04, 2013
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3 answers 2 comments
ANSWER by , October 04, 2013
It is possible you have an internal transmission problem. What does the fluid look like? it should be a clean pink color. Smell it too, does it smell burnt? If your transmission hasn't been serviced in a while I would start there. Expect to pay $100-$200 for the service.
COMMENT by , October 04, 2013
It looks good and was done at around 88k miles. It doesnt smell burt either.
ANSWER by , October 05, 2013
agree with answer #1.might be a diagnostic job for dans auto in Lowellville.i used to live there on liberty st.
COMMENT by , October 05, 2013
Dans auto did run a diagnostics on it, but got nothing and was nice and didnt charge me because of it.
ANSWER by , October 05, 2013
Have the TPS and it's circuit tested directly using a real scanner and dvom to see if both readings match. Possible ECM or wiring problem. TPS signal has major influence on engine rpm and trans. shift.