Everytime i go over 40mph it does'nt want to change gear & starts shaking.. on 2004 Mitsubishi Endeavor

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I have to put my foot hard on the pedal so it could change gear,, what can i do to fix this problem??
(1) Answer
if you have been doing this for a while, there may be damage inside the trans from this.
you need a trans shop to help you determine the failure and give you a bid.