Originally Posted by Ron Johnstone

In browsing by part number you will frequently find that newer versions of your automobile carry a slightly different number for the same part. For example, my 06 E350 shift module has an original p/n of 211-267-22-24 but the last numbers of 46-24, and 48-24 will supposedly also fit. (it is shifting fine but it refuses to go into sport mode)

I would assume that newer or higher numbers are used because the part has been redesigned, hopefully to address a needed design change, but it could also mean that it has been made with a cost saving.

Surely the pro's run into this very frequently. Any advice as to which version to buy and how can you really know what change has been made for what reason?