You might try another quart of transX... Be sure you drain a quart.....I still think that the flaring is in your B valve....I have a couple MB's doing the same thing...but mine will shift from 3rd to 4th if I let up at 20-25 mile an hour and not flare or if I manually shift it does not flare....I am going to fix it by removing the b valve and updating it....I have seen wonders happen to a 240D when it would not shift out of low gear.....went around the block several times and got up to 4500 rpm and no shifting....added 2 qts ..Owner driving and I was the passenger and we went about a block reving it up in low and braking and reving up and finally it shifted...within 10 minutes we had it out in the country and I was driving and downhill from a slow rolling start I ran it up to 80 mph....the car shifted like a new one...9 months later my friend customer is still driving it and it might be flaring between 3-4th...
so I don't think that tranX will hurt it.....just my feelings...Jim

__________________
James A. Harris