Date registered: Aug 2006
Vehicle: 99 C280
Location: Leesburg, FL
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There are many flavors of this transmission. The biggest difference is the gear ratios. Then good thing is there are two flavors. Small NAG, for V6 (4 cyl) applications, and Large NAG, for V8 applications. There are different combinations of clutches, hence all the revisions. The revision numbers xxx (722.XXX) also include the tcu programming.
The transmission you have should work just fine. The electrical portion internal to the transmission, is just a group of solenoids. No intelligence inside.
The later transmissions use a bearing between the input and output shafts. This is a great improvement, and will extend the life of the unit greatly. The roller bearing is not retrofittable to the earlier transmissions. Sonnax makes a repair kit, but usually the transmission has failed catastrophically, and is not repairable without a complete internal gearset.
I believe this change was made in conjunction with the model year 2000 shifter change. This update changed the shifter pattern, the gear encoding (from a voltage output from the shifter to actual canbus control), and the shifter safety interlock. The interlock changed from a cable actuation, to an electrical one.
What this means is if you install a late transmission in an early car, you lose the safety interlock. The car can be shifted out of park at any time. There is no provision on the later transmissions to install the interlock cable
Bellhousing bolt patterns aside, there are also about thirty different torque converters used by the 722.6 transmission. For MB applications, as long as the transmissions come from similar cars (I-4 to I-4) (V-6 to V-6) you should be good. Be sure when you have the transmission bolted to the engine block, you can move the torque converter front to back easily. If it will not move, or is hard against the flexplate, something is wrong. Do not continue, as turning the pump (torque converter) will destroy the pump.