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TH-700-R4 Lockup Converter

If you are going to be using a TH-700-R4 automatic overdrive transmission in conjunction with your TPI fuel injection system installation, we strongly recommend that the torque converter lockup function be retained since the transmissions cooling capability is adversely affected when the vehicle is operated for long periods in overdrive, without the TCC engaged. In addition, operating the vehicle in overdrive with the TCC engaged, lowers engine rpm and improves gas mileage.

Transmission TV (kick-down) cable

You must use a kick-down cable from a TPI / 700-R4 vehicle. The bottom end of this cable is the same as a TH200-4R cable so it will fit either transmission.

Wiring Information

The majority of 700s that were originally used behind TPI engines have three wires coming from the 4-pin electrical connector on the left side of the transmission. If your trans has less, more, or different colour codes than the ones listed here, it will be necessary for you to obtain a GM service manual for the year/model transmission you are working with to properly identify the components and wiring hook-up for your unit. Due to the large number of variations from year-to-year and model-to-model of the stock 700 wiring hook-ups, it is STRONGLY RECOMMENDED that you obtain a GM manual and identify the type you are working with!

The following wiring colour code information assumes that you have obtained the appropriate wiring connector that plugs into the TH-700-R4 automatic transmission from the same TPI equipped vehicle from which you obtained the fuel injection wiring harness.

The purple wire (terminal A) is the +12 volt supply to the system. The blue, or in some applications dark green, wire (terminal B) is connected to the fourth gear (overdrive) switch in the valve body. This normally closed switch opens whenever the transmission shifts into fourth gear; this informs the ECM that the transmission is operating in the overdrive mode. The tan wire with a black tracer stripe (terminal D) is the ground wire for the TCC solenoid. In the original factory installation this wire is connected to the ECM and when all preprogrammed requirements for TCC operation are met, the ECM grounds this connection to complete the circuit and activate the TCC solenoid in the transmissions valve body which then hydraulically actuates the clutch in the torque converter. terminal C remains unused in this four connector plug. For our rewiring purposes only the purple wire (terminal A) will be used to provide a +12 volt supply to the TCC solenoid. The ground side of the circuit is provided by the method described below.

TH-700 Without ECM

There are a number of ways to rewire a 700 to obtain the TCC function when the transmission is used in an application without an ECM, or when ECM control of the TCC operation is not deemed desirable. The following is one method that has been tried and tested on many hot rods:

  1. After removing the transmission pan, disconnect, remove and discard the wire which runs from the fourth gear switch to the 4-pin connector in the transmission case.
  2. Remove the fourth gear switch (normally closed) and replace it with GM #8627332 or Standard Ignition Part #PS-131 (normally open). In order to gain access to the fourth gear switch to remove it with a socket-wrench, it will be necessary to remove the 1-2 Accumulator housing which is attached to the transmission case with 3 metric bolts with a 10MM hex-head.
Be careful not to damage the gasket!
  1. Remove the TCC solenoid ground wire (Black) from the 4-pin wiring connector and connect it to the new switch . If your transmission has a 4-3 downshift switch in the +12V supply wire (Tan) side of the circuit, as most do, retain it.
  2. The fourth gear switch (single terminal) is the one on the far right (facing forward) of the rear of the valve body and the 4-3 downshift switch (two terminal) is the unit directly inboard of the fourth gear switch. Rewired in this manner, the TCC will operate only in fourth gear (OD) and will stay locked up whenever overdrive is engaged. Some 700s other than the Corvette, Firebird, or Camaro units use a fourth gear switch or a third gear switch which is normally open and can be used as is. If yours has a normally open third gear switch, it can be moved to the fourth gear port and the third gear port plugged with a 1/8" pipe plug.

After-market Kits

This is not the only method that will accomplish TCC control without an ECM, but we have found it to be effective, foolproof and, by far, the least expensive procedure, even though it does require the removal of the transmission pan. There are other methods and, in fact, some aftermarket kits are available to control the TCC function using external wiring and switches that do not require the removal of the transmission pan.

One such kit is produced by B&M Automotive Products, 9152 Independence Avenue, Chatsworth, CA 91311 (818-882-6422) and is available through most Speed Shops, Street Rod Shops, or any auto parts outlet that handles the B&M product line under #80217. If driver control of the TCC function is desired, it is merely necessary to place a push-button or on/off toggle switch in the +12 volt TCC supply line (purple wire) to the 4-pin connector in the transmission. In the OEM application this positive +12 volt supply line is also routed through a normally-closed switch, that is activated by the brake pedal, to remove current from the circuit, and thereby unlock the converter clutch, whenever the brakes are applied. For safety considerations, it is desirable to retain a switch in the system with this function.

If it is impractical to install an extra switch in the brake pedal area, this function can be obtained by using a normally closed relay, activated by a supply wire from the switched side of the existing brake light switch. As the preceding information again indicates, it is a VERY good idea to have the proper GM manual handy during this rewiring process.

Final Adjustments

After getting your TPI injected engine running there are 3 basic adjustments that should be made to ensure proper operation. These adjustments should be made in the exact sequence detailed below, with the engine warmed to normal operating temperature.

Setting Initial Timing

The initial base timing is set, after disconnecting the set-timing connector, by manually rotating the distributor, to adjust the timing to 8-10.

The set-timing connector is the snap-apart connector in the tan wire with a black tracer that is contained in the 4-wire harness which runs from the distributor to the ECM.

Separating this connector will cause a Code 42 to be stored in in the memory of the ECM. The memory should be cleared after setting the timing by removing Fuse #l for 30 seconds after reconnecting the set- timing connector.

The ECM sets the EST at a specified value when the diagnostic test terminal in the ALCL is grounded (refer Para 41. Page 13 and Para 205. Page 49 for more details on ALDL Diagnostic Modes). To check for EST operation, the timing should be checked at 2000 rpm in normal mode and then set the ECM to diagnostic mode.. If the timing changes, then the EST is functioning. A fault will set Trouble Code 42.

Minimum Idle Speed Adjustment

The idle stop screw is used to regulate the minimum idle speed of the engine. It is adjusted at the factory, then is covered with a cup plug to discourage unnecessary readjustment. We recommend checking and readjusting the base idle speed, as part of the basic set-up procedure. Before checking minimum idle speed be sure the ignition timing is correct and, be sure the throttle body is clean around the throttle plates.

  1. Pierce the idle stop screw cup plug with an awl, and apply leverage to remove it.
  2. With the IAC electrical plug still connected, ground diagnostic terminal B of the ALDL connector by jumpering it to terminal A.
  3. Turn ignition to ON position. Do not start engine! Wait at least 30 seconds.
  4. With ignition still ON disconnect the IAC electrical connector.
  5. Disconnect the distributor set-timing connector.
  6. Start engine and allow to go Closed Loop. (With the ALDL diagnostic terminal grounded the Check Engine light will blink 21/2 times per second while in Open-Loop and slow to once per second when the system changes over to Closed-Loop.)
  7. Remove the ground from the ALDL diagnostic terminal.
  8. Adjust idle stop screw with a 1/4" drive #T20 TORX socket or similar driver to obtain 450-500 rpm in Park or Neutral.
  9. Turn ignition OFF and reconnect electrical connector at IAC motor.
  10. Remove Fuse #1 for 30 seconds to remove Code 42 from memory.

Adjust TPS (Throttle Position Sensor)

Apply the following steps:

  1. Plug SCAN tool into ALCL connector OR connect a Digital Volt Meter between Circuit #417 (+) (Dark Blue wire in TPS 3-wire harness) and Circuit #452 (-) (Black wire in TPS 3-wire harness).
  2. Loosen TPS Sensor mounting screws. (#T25 TORX).
  3. With ignition ON manually adjust TPS Sensor to obtain a reading of .54 +.08 volts (.46 to .62 volts).
  4. Tighten screws, then recheck reading to insure adjustment has not changed.
If the TPS sensor was removed for any reason during the installation process it should be adjusted BEFORE starting the engine for the first time, and will then have to be READJUSTED AFTER the Minimum Idle Speed adjustment is made!

Emission Controls

The Emission Control laws world wide that apply to automobiles are making it increasingly difficult to obtain the required emission compliance to either register or sell a vehicle or to pass a vehicle emission inspection. Accordingly, we highly recommend that you retain all the appropriate emission controls when installing a TPI engine. With all emission equipment installed and functioning properly, a TPI conversion will pass any current emission requirements with ease, and with practically no adverse effect on performance.


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