GM 4L80E Transmissions: How to Rebuild & Modify

As the successor to the venerable and popular Turbo Hydra-matic 400 (TH400), the 4L80E was the next flag bearer in GM's line of automatic transmissions. While serving as the smaller, lighter cousin to the 4L85E, the abundance of 4L80E-transmissions manufactured between 1991 and 2013 ensures that these highly capable 4-speed overdrive units will be in service for years to come. Automatic transmissions are often seen as mysterious and overly complicated, but much of the guesswork has been sim...