A 727 takes a lot of effort to push backwards. My Duster is very difficult to push backwards. It rolls forward much easier than backwards. You could have some other issue too but it is probably normal. If you want to spend some time working on then remove the driveshaft and see how easy it rolls. If it rolls easily without a driveshaft then you know the problem is the trans. If it is still hard to roll without a driveshaft then you most likely have a sticky brake or a flat tire or some other such issue.