Doing this won't hurt the transmission or the torque converter as long as you don't hold it for a long time and heat up the tranny fluid. While you are holding the brake the only thing moving is the TC and the front pump and they will only heat up the fluid with no wear what so ever to the clutches that aren't turning.

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1977 300D Lost coolant while someone else was driving
1983 300D Can't run without oil
1985 300SD (gone but not forgotten)
1990 300TE 4matic Sold
1991 Yamaha Venture
1975 Kawsaki 250 triple
1974 Honda 200CL
1951 8N Ford
2008 Wildfire 650C