By the 88 model year many small improvements had been made to the green-top T-II's such as segmented fan, shoe and walker changes etc so they had almost the capacity of the earlier 7720's in many crop conditions. That machine could run for many years yet. I'm trying to remember if there was a planetary final drive option on the 6620's as there was on the 7720's...that would really ice the cake.  Have a good harvest, Von.

Jim at Dawn