Vintage auto buffs restoring vintage Chevrolets may require basic service and diagnosis of standard run of the mill 400 and 400/475 Turbo Hydra-Matic automatic transmissions of their Chevy’s that are their automotive restoration project. They may want to do the “work” themselves or their local GM dealership service department or vintage auto community trusted mechanic may just be too busy. It may be the case that their local auto restoration expert of perhaps the local “Chevy guy” is instead perhaps working on more exotic cars and components and thus has given them the short shift. Here is a “quick service” guide for quick service on 400 & 400/475 GM especially Chevrolet Turbo Hydra-matic automatic transmissions especially in dealing with diagnosis of the causes of basic and simple transmission fluid leaks.

The Chevy enthusiast may be quite hamstrung and even alarmed to find fluid leaking out of the bottom of their project car onto the pavement or garage floor. Have heart and persistence. These older GM products are not only “built like Chevies” they were solidly built, relatively simple and made easy to work on. This you might notice is unlike mainly of the domestic and imported Japanese, Asian and European newer vehicles that your shop will come across and cannot really work on in any practical sense. That is of course without specialized tools available only and at and through – you guessed the auto maker’s local dealership’s service center and their ‘factory trained” mechanics and technicians.
The Turbo Hydra-Matic 400 and 400/475 transmissions are labeled as fully automatic units consisting primarily of a three element hydraulic torque converter and a compound planetary gear set. Three multiple-discs clutches. One sprag unit, one roller clutch and two bands provide the friction elements to obtain the desired function of the planetary gear set.

The first task in this series is to check fluid level which should be fairly standard procedure for auto owners. At normal operating (non cold being driven or warmed up) fluid levels on the transmission dip stick should be at the “full” (on Chevrolets and older GM products) or in some other trucks, cars and now SUVs at the “max” or “maximum” marking. Specifically with this turbo hydra-matic setup in case of cold tranny fluid measurements the level should lie approximately