I have a 84 Bronc II with a C5. If I put it in drive it sometimes shifts and sometimes it don't but will go ok in 1st gear. It seems there is no 3rd gear or it slips bad. Reverse will usually work when first cranked up and cold, but after warming up it slips and will not back up at all. Well every great once in a while it will if reved up a little. This is a hunting buggy (no doors, top cut off, etc) so if there is something I can do like tighten the bands maybe????? to keep it going till spring any help would be GREATLY appreciated.

 

Unfortunately reverse and third use the direct drum inside the trans, your description of the problem leads me to believe that there is a problem with this drum and its ability to hold. There is no band adjustment for this, and the only fix for it is going to be to remove it, take it apart and rebuild it.