I have a 1969 as well. It does sound like you are stuck on low. As mentioned there is a handle under the dash for switching to low range. When you pull this handle it also pulls out a plunge stylecswitch which is your vacuum shifter. Sometimes your low range shifter “jump” to the front of that vacuum switch and you think you have pushed the transfer lever all the way forward (toward) engine to get out of low range, but it might be hung up on a little peg in vacuum shift plunger. Look under dash and observe how that low to high range lever works and how it interacts with vacuum shifter. Pulling low range lever toward you SHOULD pull vacuum knob out toward you too. Theory is, if you are switching to low range, you want to be in four wheel drive. If pulling the low range lever toward you does not also pull vacuum knob toward you then the lever has jumped that little pin in front of vacuum shift knob shaft. If so you will have to bend/ strong arm it back behind vacuum knob shaft.