When it gets cold outside I have trouble getting the truck to go forward until it warms up a long time. I can back up fine I just can't go forward. If I try to go forward (give it gas) my back tires will spin but the truck won't move. This is in regular drive position, not 4-wheel. After it warms up (at least 10 min. or more) it will go forward but kind of pops first. I have no trouble with it otherwise. It drives fine and shifts normal. What could be causing this. It just does it when it gets below 35 degrees. It started doing is some last winter,

I think your other rear brake is sticking to the drum. Or possibly one of the front ones. But the rears are where I'd have checked first.