Q&A

Mailbag: How to Adjust Your TV Cable to Correct Improper Shifting on a 700R-4 Transmission

Q: I have rebuilt a 1984 Suburban 4×4. I replaced the 350 with a 402 big block with 10:1 compression, and rebuilt a 700R-4 transmission with a Corvette servo.

The problem I have concerns the transmission. It shifts fine if you hammer the throttle or in open highway driving. But if you accelerate too slowly, the transmission will not shift from second to third until 3,200 to 3,500 rpm, and sometimes between 3,500 to 4,000 rpm. I have to feather the throttle to get it to shift.

Is the problem an improper detent cable adjustment? If so, what is the proper way to adjust the cable? Is the cable travel distance wrong on the carburetor? The truck has no computer, and I am using an adjustable throttle cable bracket with an automatic transmission kickdown.

A: The detent cable on a 700R-4 is more commonly known as a “TV cable.” As you have discovered, if this cable isn’t adjusted properly, the transmission won’t shift properly, if at all.

Here’s the procedure for adjusting the TV cable:

  1. Depress and hold the metal reset tab.
  2. Move the slider back through the fitting, away from the throttle idler lever, until the slider stops against the fitting.
  3. Release the reset tab.
  4. Test drive.

You may have to do the reset procedure more than once to get the transmission to shift properly. If this doesn’t cure the problem, then you’ll want to have a good transmission shop check the output pressure on the transmission pump.

OnAllCylinders works with the Summit Racing tech experts to get answers to your your automotive conundrums, you can read previous Mailbag features here.

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5 Comments

  1. i changed my carb on my sb chevy s 10 it has a700r4 and when i put the cable bracket on the new carb it didnt want to shift only at 2000 rpm the tv cable was to loose tighten it up and it works fine

  2. How about adjustment techniques for the 700R4 cable adjustments connected via aftermarket cable setups?

    • OnAllCylinders says:

      Gary, we will look to cover that in a future post. Was there something specific you were looking to touch on?

  3. Malcolm Dyer says:

    A Holley Transmission Kickdown Bracket 20-121 was needed on my Speed Demon carb to get the geometry right.
    It´s not just TV cable being pulled by carb linkage the arc of the TV mounting point on the linkage.

  4. Robbin Johanson says:

    A friend and I just installed 700R4s in my ’65 Biscayne big block and my ’70 Chevelle SS454. Adjusting the TV cable is straight forward. However, the most challenging part is making sure the TV cable is connected to the primary throttle arm with an arc of 78 degrees and at a distance from the center line of the primary butterfly shaft of 1.110 plus or minus .015. This precision makes for correct “pull” on the TV cable. If the car shifts from 1st to 2nd too early, this can be harmful to the transmission. To increase the RPM at shift, adjust the cable to be tighter at no throttle. I’ve found that the TV cable is best adjusted when there is about an 1/8 to 1/4 inch of tension on the TV cable at no throttle…

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