GM automatic transmissions quite literally rule the world. The venerable Powerglide has been the gold standard of durability and efficiency in drag racing since the ’50s, and the workhorse TH400 has ...

For the price of the trans pan, valve body, and separator plate gaskets, the firmness and quickness of GM Turbo 400 upshifts and downshifts can be dramatically improved, according to Darrell Young's ...