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This car came to me needing Hospice, dying. I got it for a project car which is going back together very well. I only have a Haynes Manual and the Corvette Aim.
I see in the Haynes Manual what is called a Down Shift Cable, and in the AIM, a detent control cable. This is missing on my car. I see in Haynes Manual that one end is fastened to the throttle lever on the carb, the AIM shows the other end
attaching to the tranny just rear ward of the vacuum modulator. I see the adjustment procedure in the AIM.
This is the first Auto Tranny I have ever owned in my 55 years of driving. Do I understand correctly, that at the Carb, I will end up with 2 cables attached to the throttle lever. One cable going from the lever, thru the fire wall to the go pedal. The other being the detent control going to the point on the Transmission.
Help me understand, I thought that the vacuum modulator on the tranny took care of all shifts ?????
This car came to me needing Hospice, dying. I got it for a project car which is going back together very well. I only have a Haynes Manual and the Corvette Aim.
I see in the Haynes Manual what is called a Down Shift Cable, and in the AIM, a detent control cable. This is missing on my car. I see in Haynes Manual that one end is fastened to the throttle lever on the carb, the AIM shows the other end
attaching to the tranny just rear ward of the vacuum modulator. I see the adjustment procedure in the AIM.
This is the first Auto Tranny I have ever owned in my 55 years of driving. Do I understand correctly, that at the Carb, I will end up with 2 cables attached to the throttle lever. One cable going from the lever, thru the fire wall to the go pedal. The other being the detent control going to the point on the Transmission.
Help me understand, I thought that the vacuum modulator on the tranny took care of all shifts ?????
Thank You
8Valve
You're getting the 4 cables confused. You have a throttle cable that goes from the top of the bell crank to the gas pedal, a downshift cable that also attaches to the bell crank, and the detent cable that goes from the shifter to the lever on the left side of the transmission. That is the cable that puts it into PARK, R, N, D, 2, and 1. Then there is a short "lockout" cable that prevents putting it into gear unless the key is turned ON.
Ok, I was confused. I am referring to the downshift cable. I assume since that cable is missing, the tranny will not downshift when the go pedal is pressed to the floor.
My main confusion is the difference between the vacuum modulator and the downshift cable. I 'thought' the vacuum modulator controlled the shifts.
So now, I will order the downshift cable and move forward.
Ok, I was confused. I am referring to the downshift cable. I assume since that cable is missing, the tranny will not downshift when the go pedal is pressed to the floor.
My main confusion is the difference between the vacuum modulator and the downshift cable. I 'thought' the vacuum modulator controlled the shifts.
So now, I will order the downshift cable and move forward.
Thank You
8Valve
When I was a kid, we all called it a kick down cable. There is 2 styles. They both go to the trans but the other end goes to the carb using a bracket to hold the cable. Very similar to a TV cable used on 700R4 trans or the style I like to use goes to the gas pedal. Most GM cars have the knock out plug in the firewall and an attachment point on the gas pedal. To be honest, I'm not sure if our corvettes have these provisions but all other GM cars in the 70s do.
The kick down cable does just that, senses full throttle and the governor dictates how many gears it will drop down. The vacuum modulator is used to up shift the trans at light throttle. It senses vacuum and lets the trans up shift. There's a lot more to it but that's a basic idea. You can adjust your up shift points by turning a tiny screw in the modulator. Located in the vacuum port inside the modulator.
You should start by making sure which trans your car actually has. A TH400 has no kickdown cable but uses an electric solenoid for that purpose. 79 came with the TH350, but no telling what other owners have done.
Thank you for the help. I understand the difference in the kick down and modulator. I will also check the pan against the picture posted to be sure I have a Turbo 350
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Turbo 350 Detent Control Cable
