[65comet]

Tranny, how many miles? Last time trans filter and fluid changed? Checking fluid level when hot/running on flat surface, is it close to the top of the hatched area of the dip stick? It could be low fluid and when you go to steep angles it might be starving for fluid in the correct areas of the trans.
4X4, correct full time operation. Where you exceeding 35 MPH? The designers in their wonderful wisdom decided that you shouldn't need to be in full time mode when you go above 35. It will automatically kick out and go back to auto detect for wheel spin engagement of 4X4. But returning to slower speeds it doesn't usually return to full time mode. So they have it flashing the engine light and you have to manually reset the switch to auto, wait till it stops flashing, then you can switch to full time 4X4 again as long as you stay under 35. I always turn mine back to auto when I get above 25.