You can think of this trans as basically a TH400 with a 25 percent overdrive tacked on. The 4L80E transmission was mostly used in 3⁄4- and 1-ton trucks and larger SUV applications beginning in 1991. The “E” means that it must use an electronic ECU for control, as it will not function without it. The trans has experienced multiple minor upgrades over the years, with the newer boxes being a bit more attractive, but all the versions can be made to work well in a performance application. The addition of electronic control and overdrive adds roughly 50 pounds and a slight amount of width over a TH400, but for the most part, any floorpan that can accommodate a TH400 can also fit a 4L80E. Also, the 4L80E transmission is typically about 4 inches longer than a TH400 (depending on the length of the extension housing), but the trans mount is located roughly 11⁄2 inches rearward.