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What you describe sounds to be a problem with transmission/motor. This is not a repair that would prove to be economical. Depending on what is found when you pull this apart you are likely looking at $250.00 or more in parts. This is not an easy job even for a trained servicer.
If you have a servicer who is experienced do this job, it will likely run $400.00 or more.
Please let me know if you would like more information and/or clarification.