I have a 4L80E in my burban, and after 81K, I might be getting a new one soon. Long shifts, hard shifts, and a shimmy noise. Of course this is just one of hundreds of thousands made. Its good on the highway, but I have a 327 and 3.73 gears in that with 17" rims and have gotten as high as 21 MPG at 80 MPH. But like I said its different from you. I personally dont like them. And its an electronic version of the 700R4 from what I understand, same gearing, just with a computer. If your gonna go all out, get a Allison 1000, There is a 5 speed version, and the more common 6 speed auto. They are pretty much indestructible, and they have an outside filter and drain plug!