Which gearbox for which series? (1998 w140)

[DoctorGee]

There is so much detailed information on changing ATF in the "sealed for life" MB 'boxes on the forum- it's brilliant. I have decided I need to change mine. There is no record of a change in it's service history and it's got 162,000 miles on the clock. It sometimes goes into limp mode after a roundabout or stopping at lights and it needs a back & forth shift to get into reverse most times.
Can anyone tell me how I can identify which 'box I have? The car is a 1998 W140 (S280). I hope these ones have the TC drain plug..
By the way, how do you open or break the seal on the filler pipe I finally found?

Thanks all,

Greg.

 

[television]

All MBs after mid 96 have the 722.6 box. drain plugs were slowly deleted across the range so that by 09-99 no drain plugs were fitted, just break the thin seal and get a new one from MB if you wish