Stopped at red light then no forward drive , reverse perfect. on 2009 Chevrolet HHR

When finally engaged 1min approx , shifts normal all gears after 20km. Will climb steep grade at 20km with no slip. Replaced both shift and pressure soleniods, filter and fluid 6 . Still- reverse engage and full torque. Forward slip in all forward settings at first till late engagement and in gears when pedal hammered down sudden, other than that drives forward perfect. NO CODES have ever recorded - computer cleared with code reader twice and battery totally disconnected 30mins. Possible cause , wondering if forward valve stuck or blockage in - please offer things to check that might cause this - thanks greatly

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1 answer
If that is the 6 speed automatic trans, there are 2 engineering documents for that condition. 1 document has not even been released to the service community as of yet. Replace the transmission control module and program the latest calibration. Also, if you are mechanically inclined, replace the 3/5 wave plate and piston seal.