Hi All, I have a 99 ML320 that is not shifting properly. While driving lets say 20miles per hour and I floor it, the RPM revs up (5000 RPM) yet the car bogs down and keeps on driving at 20miles an hour. Once I release the gas paddle I feel and hear a thug sound from the trany. Has anybody ran into this issue.

Quick background: 1- The Air Mass sensor was replaced not too long ago due to check engine light.
2- The gas paddle assembly was replaced by the dealer because they thought it was causing the shifting issue. (well it came back).
3- the fuel injectors were cleaned as part of the troubleshooting steps (To no help).

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THX
Smouhanna