The transmission vacuum modulator on my recently purchased 1987 300TD doesn't hold vacuum. I tried replacing it last night but was unsuccessful due to the space issues and none of my assortment of 5mm hex wrenches fitting the bill. I did remove rear transmission brace to gain a little bit of room but to no avail.

I've done this job on a W123, which was difficult but do-able. I know other people on this board have replaced theirs so I'm hoping someone has some tool tips or other suggestions on how to accomplish this on the W124 diesel models.