X5 Diesel Gear Box Change

[MDEF]

Just Spoken With Bmw Mechanic,after Replacing The Transmission Control Module, Now They Say That It Works But After The Engine Warms Up The Gears Start To Slip...so He Says They Have To Change The Gear Box !!!

They Claim They Have Checked All The Electronics, Test, Last Version Of Software, Etc And That The Gear Box Is The Only Thing Left.

Any Clue If This Is Correct.?
Are They Missing Something?

The Car Is Only 2 Years Old, Before The Message " Trans Failsafe Prog" Came Up None Of This Had Happened.

Im Really Thinking On Getting Rid Of The Car...