Other Articles - December - 2018

A Look Back: Adjusting the THM700-R4 Throttle Valve Cable

The 700R4 has been around for over 30 years, and yet they still show up in shops all across the country. For veteran builders this unit is pretty straightforward, but for the new guys who are thinking, “where’s the computer?” some issues might pose a problem.

Step 1: With the engine off, disconnect the TV cable from carburetor or throttle body.

Step 2: Have an assistant hold the gas pedal to the floor. With the pedal on the floor, make sure the throttle is opening all the way. You need to verify this before making any adjustments.

Step 3: Pull on the cable end and make sure it moves smoothly in both directions. If it doesn’t, suspect one of these problems:

  • The cable is damaged and needs replacement.
  • The TV plunger or internal linkage has a problem inside the transmission.
    Correct these problems before moving forward with your adjustment.

Step 4: Press and hold the release button on the cable, and push the inner jacket all the way back toward the bracket.

Step 5: Reconnect the TV cable.

Step 6: Press the release button while your assistant holds the gas pedal to the floor.

Step 7: Release the button and let the throttle return to the idle position. Mark the cable, just in case you lose this adjustment.

This is called the coarse adjustment. From here, you’ll need to drive the vehicle before making the final adjustments.

Step 8: Test drive the vehicle at light throttle. The 1-2 shift should occur at about 15 MPH. It should shift 2-3 at about 28 MPH. For now, don’t worry about 4th gear or lockup.

If the transmission shifts late, pull over, pop the hood, and grab the cable adjuster with your left hand so it stays in place. When you press the cable adjuster release button, pull the cable adjuster forward a few clicks. This will cause the transmission to shift earlier.

If the transmission shifts too early, grab the cable adjuster so it doesn’t move, press the release button, and move the cable back toward the bracket a few clicks.

After you get the transmission to shift at the right speeds for the 1-2 and 2-3 shifts, you’re ready to verify the transmission has a full-throttle, 2-1 downshift:

  • Accelerate at light throttle.
  • As soon as the transmission makes a 1-2 upshift, press the throttle to the floor. The transmission must downshift to 1st gear.

Don’t deliver the vehicle if it has no 2-1 downshift. This means you need to make a fine adjustment to the TV cable, regardless of the shift speed adjustment. If the transmission won’t downshift 2-1 downshift after the 1-2 upshift, adjust the cable back one click at a time until you have a 2-1 downshift at full throttle. Now you’re ready to verify 4th gear and lockup.

If you follow this adjustment procedure to the “T,” the transmission should shift properly, and it won’t fail due to incorrect TV adjustment.


This article was provided by our friend and ATRA Member Paul Townsend at Paul’s Transmission and Repair.