2000 Trooper (Oz=Jackaroo) 3 L Turbo Diesel Driveability

Had this since new, now 110,000km and for the past 4 years I've had a fault (MANY TIMES!)thats fixed for a short while but keeps coming
back..Its an AUTO...You drive at about 40mph(65km/h) and your in overdrive with the torque convertor in lock mode doing about 1300rpm...ok so far.. then you accelerate gently..but not hard enough to unlock the convertor or drop down a gear....and the acceleration is midly rough, jerky, not smooth...it even shows up on a dyno graph. Now I've driven other identical models and they dont do it so I know its my car. What do you guys think? ps..The dealer has replaced a list of items the length of your arm...would be good if someone out here has come across this problem.....I half suspect that similar owners may just put it down to being a Diesel....Thanks
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