There is a roll pin in the handle ( it's in the part closest to the glass) just drive it out carefully with a small punch and a hammer. You should take the vent window out to do this. Once you have the handle off you will see a spring with a wavy washer behind it, the spring might be weak from time or the little plastic nib on the end of the handle might be worn down.
Handle's for Vent Window's
Does anybody know where i can get the handles for the vent windows on my 85 D350? If someone could also tell me how they come off, that would be helpful too. My old 77 had a screw that held them on, these i have no clue. 
