Restating my post 7 above, in what direction do you have free play. The direction matters.

After inspecting the yoke and nut, I should be more specific:

No play at all between yoke and shaft. Yoke not loose; i.e., no worn or wobbly splines. (additionally, nut not loose).

There is the normal play - in the rotational axis - when in park. Not a concern. IE, feels like a few hairs of play in the gears.

However, the shaft will move ever so slightly in any direction - up/down, left/right - in what might be called the car's coronal plane (!)

There is the corresponding wear/slop in the output shaft seal, which has resulted in a slow leak of trans fluid. Does a standard 12-pt socket fit on that damned nut in there (mine is not the slotted one)? Anybody know the size?

Stretch, you've done this work on your 124, I think. Care to weigh in?

__________________
'83 300 SD
'05 E320 4Matic
'06 BMW 530 xi
'68 Triumph TR 250 - The only car I ever loved more than the Mercedes; who needs electricity, anyway? - Damn, why did I sell it?!
'59 Jaguar 3.4 'Le Chat Noir' - Damn, why did I sell it?!

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