Transmission flange nut removal - 380SL

While the transmission is out of my car I would like to replace the front and rear seals. Automatic transmission on a 1982 380 SL. The rear seal can not be replaced until the flange is removed from the shaft. I was unable to locate a tool with the four "teeth" that fits the nut- rather than being a hex nut it is a design that uses four slots arranged 90 degrees to each other. I have fabricated a tool but so far have been unsuccessful in breaking the nut loose. I am reluctant to apply too much pressure because I don't know if I am dealing with right or left hand threads. None of the threads show on the shaft so there are no visual clues. Does anyone know which they are- right or left hand??? Thanks

Randy