My transmission is causing me some grief. I hope someone can give me some ideas as to what may be happening. The transmission was rebuilt about 5000 miles ago. The Yukon has been sitting for about 7 months. I just replaced the motor that had a blown bearing. My problem is that when the truck is in OD it shifts through 1 - 2 then shifts into neutral. I drove it in first .. no problem, second .. no problem, put it in third and it goes to neutral including OD. So I have reverse, first and second, but no 3rd or OD. Any ideas?? Please help if you can. I have no codes coming up.