Help identifying TV cable

Blue-88 · Mar 2, 2023

Looking for some guidance. I have a 1988 c1500 305 auto. I finished some upgrades to the TBI (new injectors and a spacer). I took it for a test drive and can notice some gains, but when I floor it the trans doesn’t downshift into a passing gear. I figured I needed to adjust the TV cable and popped the hood and I don’t see a TV cable. I have two cables coming off of the TBI, the throttle cable and another cable below it that goes to a plastic box on the firewall. Inside that box is a circuit board and a spring tensioned spool. I’m guessing this is the TV cable for that model year, but I do not see anyway to adjust it. When I pull the throttle open, slack on that ribbon doesn’t get taken up by the spool. Anyone else confused?

L31MaxExpress · Mar 2, 2023

TH400/3L80 trans?

PlayingWithTBI · Mar 2, 2023

Blue-88 said:
the throttle cable and another cable below it that goes to a plastic box on the firewall. Inside that box is a circuit board and a spring tensioned spool.

That plastic box s/b your cruise control. Does your shifter have P R N OD D 2 1 on it or does it just have 3 forward gears? If you have the 700R4, and cruise control, you should have 3 cables going to the TB

Blue-88 · Mar 2, 2023

I was surprised I didn’t see a TV cable. It is a 700 trans I believe and D 2 1 with no cruise control.

Blue-88 · Mar 2, 2023

There is a place for the cable, just no cable…before I removed the cables I had a passing gear. I was thinking it just needed an adjustment after install and no adjustment points to be had

PlayingWithTBI · Mar 2, 2023

Blue-88 said:
It is a 700 trans I believe and D 2 1 with no cruise control.

Well, at one time that truck had cruise control. If your column only has D 2 1 you do not have the 700R4, probably TH350 (3L60) since it's a 1500. The square hole on the plate under the throttle cable is where the TV cable would go, if you had a 700R4. Look for a vacuum line going to the trans for your kick down.

PlayingWithTBI · Mar 2, 2023

It took me a while to find this picture of my 88 C1500 Silverado;

The red arrow is the Throttle Valve cable
The green arrow is the Throttle cable
The blue arrow is the Cruise Control cable

You must be registered for see images attach

Schurkey · Mar 2, 2023

Perhaps a moderator will move this threat to "Transmissions".

A TH350 should have a kickdown cable to go along with the vacuum hose to the modulator. Looks just like a TV cable, but only affects kickdown.

A TH400 would have the modulator, and an electric switch (by the gas pedal?) to provide kickdown.

But in any event, if the shift indicator shows three forward gears instead of four, it's not an overdrive 700 transmission.

A picture of the trans pan from below (to show pan outline, or pan-gasket shape) would tell the tale.

Blue-88 · Mar 2, 2023

There is a vacuum line from the side of the trans to the intake manifold behind the TB. I will post a picture of the pan to double check what I’m working with. But the little rubber connector that plugs into the intake was half way off. After plugging it back in I was able to get a downshift at wot. Is there a way to adjust the this setup?

PlayingWithTBI · Mar 2, 2023

Blue-88 said:
Is there a way to adjust the this setup?

If I'm not mistaken you can adjust shift points by changing weights and springs on the governor but, someone else will have to confirm that.

Help identifying TV cable

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