Thread below got me to thinking about the JD 4020 and if I recall correctly they had either a Power shift transmission or the Syncro Shift (I think it was called that). 

Does anyone know how well the powershift held up to hard field work loads?  Could you commonly shift up or down under a hard load in the field without causing transmission damage?

I did some work for a large dairy off and on when I was a kid and they had a JD 4020 with the powershift and that was the handiest thing I had ever seen.  I'm just curious how well they held up compared to a more conventional tranny.