Torque Converter Explaination


[Index] [Part 1] [Part 2] [Part 3] [Part 4] [Part 5] [Part 6]


Notice: 

The following information and the opinions expressed here are directed at regularly driven street vehicles, not race cars! If you have a race only application, you certainly don't need a lock up converter, but you may wish one if you feel direct driving during a race would be beneficial. If you have a race car disguised as a street car, you definitely need a lock up converter!


Let me state up front, we as a company, believe very strongly all street applications will benefit tremendously by using the lock up converter feature. In our opinion, a correctly understood and properly used lock up converter clutch offers tremendous benefits and has no downsides (other than possibly a small weight savings and some possible cost differences). Furthermore, we feel that not using a lock up converter has inherent negative effects that are undeniable and will lead to a shortened transmission life. These downsides are easy to demonstrate and will be explained in detail in the following sections. We have heard lots of arguments why a lock up converter shouldn't be used but never heard one that makes sense to us. There is a lot of companies that will tell people these clutch mechanisms are weak and prone to failure. We have been building and installing only Th-700R4 and Th-2004R transmissions for over seven years and consider these converter clutch mechanisms to be almost bullet proof if built and used correctly. If other sources don't have the same success with their converter clutches, maybe they should find the problem and correct it instead of advising their customers to eliminate one of the greatest features available in automatic transmissions since the development of the torque converter itself.

The purpose of this technical write up is to help our customers understand what the torque converter "lock up" clutch function is, how it works and why it is so essential to the overall efficiency and longevity of these overdrives. This Torque Converter section of our web site is in seven parts. We have tried to set up this section to allow the visitor to access any single part listed below for clarification of only certain areas that they may not fully understand. Feel free to start with part one and go through this whole explanation from beginning to end. If you don't necessarily want an in depth understanding of this lock up system, just wish to purchase a system to control it, please feel free to go directly to the seventh part and just order the system you need. Our kits come with complete wiring instructions plus we have a step by step installation guide and schematics for on line viewing in part six. I would advise you to go to part 4 so you will at least understand why it's so important and how to properly use the system.


  • Part 1 - Describes all the major torque converter components.
  • Part 2 - Describes only the mechanical components used for converter clutch lock up.
  • Part 3 - An explanation of the electrical and hydraulic control circuits.
  • Part 4 - Describes why lock up is needed, how to control it and when it should be used.
  • Part 5 - Describes the two complete electrical wiring methods we offer and how to choose the one right for your application.
  • Part 6 - Step by step wiring installation instructions and schematic drawings.

  • Click here for our wiring section
    * Purchase wiring kits
    * Installation instructions
    * Wiring diagrams