I called myself looking around, but didn't find any threads that might pertain to my problem. Any help would be much appreciated. I have a 2001 Chevy Silverado 5.3L with a 4L60E. I had the tranny worked on (supposedly rebuilt) a while back and it started exhibiting the following problems not long thereafter. I went back to the mechanic and, well, it was a "cash" transaction, i.e., no invoice and therefore no proof, and there was a little bit of a falling out when he wouldn't make it good. When I shift into drive, I feel the "clunk" of it going into first gear, but when I give it gas to go, it doesn't move until it gets to about 900 rpm or so and then I feel another "clunk" and it starts moving, like it wasn't really in gear to begin with. It doesn't do this when I first crank up in the morning, only after driving a few miles and the tranny is warmed up a bit. I can put it dfirectly into second and it starts off normally. It also has another problem which may be directly related. When going at highway speeds, if I start going down an incline and don't give it gas to "keep pressure" on it (which speeds me up), it will shift out of overdrive. Even on flat stretches, if it doesn't have pressure on it, it can shift out of OD. As long as I'm going uphill, it won't do it. Thanks in advance for any suggestions.