starter spinning but is not engaging to flywheel

Please excuse the length of my posting...I have an 05 that started to develope a problem since Christmas...I live in a cold climate and it may have something to do with the deterioration of my starter. My truck developed an intermittent start problem where the starter would spin but not engage . I would turn the key to off and try again and it would engage and fire up.. I brought it into my shop, cleaned the terminals, charged the battery, it wasnt down too much, then when charged I did a load check and it said the battery was fine (its only a year old).. I left my truck in the shop for about 4 days and thought it was a good time to clean it and vacuum it..I washed it before i brought it in so possibly i got something wet underneath, but when I went to fire it up again it didnt go and after about ten flicks of the key, it finally engaged but the same every time I tried to start it.. So I figured it must be the starter and got a friend to help me take it out.. I called for a new one at a NAPA store and he asked if I was sure it was the starter because he never heard of one going and recommended I call Nissan and find out what it could be. I called the dealership which is 210 miles from me (the closest one) and talked to a mechanic. He told me since the Titan was introduced they never changed a single starter! He told me to bring it in to get it diagnosed. Visually the starter looks fine, not a mark on the gear teeth after 79000 miles. You spin the gear by hand and it smoothly moves the gear outwards to an engaged position..So I figured I should maybe put it back together and plan a trip.. Next day, I had meetings and my buddy came over and put it back in, he didnt think of trying the starter on the bench by using a set of booster cables directly on the solenoid to check for function , and he reinstalled it.. So when I got home I find out that now it wont engage at all, it spins when you turn the key but no engagement.. I had read the tsb about the connector on the side of the tranny getting corroded or damp but it is a hard thing to dry out.. I am almost thinking about changing out the starter and thought some one here may give me some new direction. I have not tried to shuffle the relays around in the EPDM yet or wiggle wires under the dash likeothers have posted but will try tomorrow.Thanks in advance for any recommendations.