Nissan A32 cefiro 2.0 auto gearbox overdrive problem

Hi carsifu's,
My nissan a32 cefiro revs up and down while overdrive is swicted on... The overdrive seems to be slipping, the problem started after gearbox rebuild. How to check the cause of this problem, I heard it may be because of tcu? Can someone help me shed some light on this problem. And also can recommend to me any gearbox specialist in kuala lumpur/ ampang area ? :confused:
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