I think you have an AD4 transmission. check id. tag on filler tube bolt on front of transmission. If so the fault will be the forward clutch. 4th gear will be fine and will slip on kickdown. This clutch is on in 1,2 and3. Box overhaul required.
mags
March 2010
I can answer this question...
How do I fix autobox on Renault megane scenic automatic?
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