I estimate about 2 mm. I remember my 4 speed having the same issue as well, and it runs fine. I was hoping to root out any issues with this one before installing. I may just be installing it and hoping for the best. I did just get the bearing though thinking it was like the other style and accessible from the front of the transmission. It was pricey. the transmission guy says its about 4 hours to get it in. it all has to come apart to get at that bearing,according to him.
Its a roller ball bearing, no taper. It cost me over 2 Benjamins. I could just keep it for another time i guess. I have no specs on the amount of play allowed. the haynes manual says .01 mm but that may in and out play i have only up and down.

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Chris
84 280sl
82 300d euro