If you do it on any transmission that is synchronized,you are putting the synchros to the test and they will not last too long. As stated above the 5600 is not a good transmission to do it with as the synchros can be problematic at times in these. If you do it and actually can get away with it, When someone else wants to drive it and the synchros are burned,up floating will be the only way you will ever get it in gear.