On a recent excursion to Mississippi, CIRCLE TRACK swung by the TCI plant and got a first hand look at the process for building a TH350. Fitted to millions of street cars, turbo-hyrdomatic 350s are lightweight, easy to install, and lend themselves well to engine and transmission swaps. While in stock form, they are best suited for use behind mild small blocks and smaller engines such as V6s. However, TCI has a line of TH350s that can handle over 600 normally aspirated horsepower. That beefiness makes the TH350 the trans of choice for many street/hobby stock classes around the country. We were so impressed with TCI's operation that it gave us an idea, but you'll have to stay tuned to the next issue to find out what that idea is. So until then check out TCI's process for building a TH350.
 One of the first things undertaken...  One of the first things undertaken is the installation of the planetary. |  Here is an underside view...  Here is an underside view of the transmission where the valve body bolts to the case. |  TCI's front pump assembly...  TCI's front pump assembly uses four Teflon sealing rings (the white and orange rings). Stock TH350s from the factory come with five cast iron sealing rings. TCI replaces the cast-iron ones with Teflon because Teflon will expand and create a better seal. In addition, TCI leaves the middle ring off which applies more pressure to the direct clutch pack and, consequently, holds better in high gear. |
This is the direct drum. |  Here are two views of the...  Here are two views of the forward drum. |  When you turn it over, you...  When you turn it over, you can see where the clutches are in it. |
 The race in the intermediate...  The race in the intermediate sprag assembly on the direct drum is normally the weakest link in a TH350 transmission. |  TCI solves the weak link by...  TCI solves the weak link by replacing the stock race with an aftermarket heat treated piece shown here. |  The rear planetary gears awaiting...  The rear planetary gears awaiting assembly. |