that is a great trans article but its the incorrect info - but yet they are similar the 300D is different BUT my guess is the clutches are gone and or the seals are brittle ( like stone ) and has led up to this the guy from Washington offered to help you HELLO -- the kit is around 300 bucks we in my shop in jersey always for the diesel cars replace the valve body plate with a re program kit ( trans go ) it fixes almost every thing that is wrong with the 123 trans - reason being it relies on the modular pressure to adjust both the when and how it shifts the info sent up above is the later unit and it has a boden cable for the when it shifts, and is way easer to set up when done - take the unit out and let the guy take it apart high millage diesels or gas cars always do this 150 to 200 thous miles depends on city or highway driving -- jz