You need to determine if its flaring or actually slipping. The flaring seems to be a vacuum issue and is more like the the tranny is hunting for the gear rather than slipping or so I think.

I am having that exact problem on the 2-3 shift, however overall, the tranny seems to be working very well. I am about to swap the filter and fluid and debating whether I should replace the actuator in the process. So I will piggy back on your thread and see if we both can't get some clarity on the issue. I have a 88' 300SEL, guessing we have identical running gear.

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1981 300TD
2005 C55
2004 E500
1999 ML430
1992 400E
1998 C43
2001 SL500
1988 300SEL
1986 190E 16V
1991 190E 2.6