I have a '94 C220 which shifts nicely for the first 10 minutes of driving and then develops a harsh upshift from 2nd to 3rd. The downshift is good and all other shifts are good.

I managed to borrow anther valve body and was able to confirm that the problem was in the valve body.

I have checked the accumulator springs and none are broken.

I have heard from someone about drilling a hole in the accumulator for B1, but would like to hear other ideas before trying this.

I would really appreciate some knowledgable advice.