Mine is a 4+3 which I will state it is a 4 speed with overdrive. I never kick it down since engine is modified engine 350 HP with a 100 shot of N20. To achieve OD I depress clutch and hit the OD button. Now I am replacing the Holley Projection manifold I have on now with a single plane and port fuel. I was wondering if anyone knows how to prevent the kick down of OD and solely use the manual switch.

 

After you go into 4th gear and want to cruise at 65 mph or better for a while, turn the overdrive on and use it as a 5th gear. That's what most of us do with our 4+3 transmissions. Don't know of anyone who uses the 2nd and 3rd gear overdrive option. Just consider your overdrive as a 5th gear and definitely use your clutch when shifting in or out of overdrive. It provides a much smoother shift and is very easy on the overdrive unit.

 

Hard wire the switch to control the OD relay. Take the ECM out of the picture. I did this when I switched my ECM to Megasquirt.

 

85 4 + 3 #8040. Kick down cable pulled out of the trans at least 5 years ago. Kicks down from over drive just as if the cable was connected. Info from my shop manual states from section 7B-2:

"The ECM is programmed to control the shift solenoid and thus, the entire overdrive unit. It does this by monitoring both vehicle speed and throttle position. The overdrive mode cannot occur when the 4- speed transmission is in first gear. It can, however, occur in the remaining three gears. Rapid acceleration will cause a shift from the of drive to direct mode. When a cruising throttle position is then used, the overdrive mode is restored in fourth gear, but it will not return in second or third. Overdrive is automatically engaged at speeds above 110 mph. The overdrive mode can be forced off by means of a switch on the vehicle console."

The word "cruising" is spelled "crusing", so you know I'm quoting the manual for sure.

It does not state anything about cable function, but it is there I most certainly agree, and must do something. But I'm not sure what since it kicks down like when it was connected. And, in the diagnoses chart under Overdrive Inop,it says nothing about the TV cable. In harsh up shifts, harsh downshifts, soft up shift and soft downshift, it mentions TV mis adjustment or stuck TV valve. But for no downshift, it only states ECM, throttle position switch.

 

Thanks for the info, this is my first vett I'm learning as I go. I've ordered the gm service manual for more info. My speedometer is not working what should I look at first?