Automatic transmissions are the most fascinating mechanical contraptions in automobiles, with insides chock-full of beautiful precision-machined components that would look at home in a NASA spacecraft. This video showing a Chevy Silverado’s heavy-duty Allison transmission undergoing a rebuild will leave you in awe of the sheer complexity of it all.

While popping around YouTube yesterday, I landed on a video from someone named Truck Master showing an Allison 1000 six-speed automatic transmission out of his heavy-duty, Duramax diesel-equipped Chevy Silverado undergoing a rebuild. The vehicle was apparently leaking from its transmission, and though he’d recently had the trans rebuilt, the host had a shop take a look at the insides. It appears that they discovered a few issues.

    Per the video’s description, the work is being done at a transmission shop called Ryan’s Diesel Service in Wisconsin—an outfit that appears to be run by wizards who have clearly mastered the art of mechanical magic. Between all the clutches, snap rings, shims, bushings, seals, bearings, and hubs, there’s just so much going on in this thing that anyone who can properly rebuild this thing must be a genius. Just watch how the rebuilder measures clearances and inspects bushings—it’s surgical.

    I’ve seen the insides of automatic transmissions before (here’s a look at some Aisin cutaways I spotted at the Paris Motor Show), and I’m familiar with automatic transmission operating principles (you can read my article on how an automatic transmission works here), but to see one rebuilt in this much detail is borderline pornography, and further confirms my belief that automatics are among the most mechanically fascinating contraptions in cars.