Richard, comparing yardages from the Legend tees to the TM tees, you come up with this...I didnt do Oakmont as I dont play it often, so I dont care lol.
Bethpage Black sees the smallest difference in distances overall. The front 9 is an average of 15yds longer per hole, and the back 9 is an average of 18yds longer per hole. This number is so small because a lot of the par 4s play nearly the same, just at different angles, but the par 3's and 5's are significantly longer from the black tees.
Kiawah Island- Front 9 averages 32yds longer per hole from the black tees, and the back 9 averages 46yds longer per hole. Needless to say, quite the change, Kiawah is beastly from the black tees. #13 plays 102 yards longer from the black tees.
St Andrews- Front 9 averages 33yds longer per hole, while the back 9 averages 32yds longer per hole.