More freedom out of your 4+3

[corvette66]

Free upgrade on 4+3 READ THIS!!!!

101 Projects for your corvette A book i read at Barn & Nobel.

They show you a way to get more control out of your 4+3. A free MOD, all you need is a 1/2" piece of wire. What it will do is make your automatic Overdrive a manual Overdrive. If you have the overdrive unit you know that it will only engage in 2-4 gears and kicks in and out when you accelorate. Well this mod will give you a full maunal trani.

On the driver side of the 4 speed box (T-10), right below the shift linkage, there is a plug/switch for 2nd gear. Called the 1st 2nd gear switch. Right next to it (closer to the motor) is the 3rd 4th gear switch. Pull the plug off the 2nd/3rd switch only and tie it up somewhere cause you won't be needing it anymore. Then run a jumper wire accros the 2 prongs on the switch itself. The switch is still in the side of the T 10 case. you only remove the plug. So by attaching the jumper wire accross the 2 prongs it is always going to be a complete circut in other words.
What this does is fools your computer into thinking you are always in 2nd or higher gear. So You can engage the OD in 1-4 instead of 2-4, also you have full control over the OD, the OD can only engage when you press the button in the car. 100% manual!!!!! Now we can call it the Doug Nash 4+4 8 speed

 

[8388]

The best way is to bypass the ecm completely and have an on/off switch near the shifter on the console. You really never want to engage the OD unless the car is traveling over 40 mph. The pump inside the unit is not effecient at speeds below 40.

On my recent overhaul, I'm also adding another in line cooler. Excessive heat is another major contributor to a short lived OD unit.

 

[corvette66]

hmm

yeah i have not try'd this yet. but i might IF and when i get my OD back on track.

 

[Top]

8388,

How do you bypass the ecm completely? Mine is an 86 and I have no wire on mine.

Thanks in advance

 

[corvette66]

yeah

well i just went out and checked my wiring harness and i don't have the plugs either. hmmmm i guess i won't be doing it either. must be an 86 thing

 

[rrubel]

Yup. Lucky us 86 owners... the only year where the ECU exclusively controls the overdrive. No wire...
[RICHR]

 

[8388]

The single wire going to the driver side of the tranny (note, not the speedo sensor) is the wire coming from the ecm. This is the wire that needs to be cut. Get a toggle switch, mount it somewhere near the shifter, then connect the switch to a positive lead and the other side of the switch goes to the tranny. Thus, the only way the over drive can be activated is when you turn the switch on.

 

[corvette66]

hmm

oh yeah? good news for us 86ers

 

[rrubel]

The single wire going to the driver side of the tranny (note, not the speedo sensor) is the wire coming from the ecm. This is the wire that needs to be cut. Get a toggle switch, mount it somewhere near the shifter, then connect the switch to a positive lead and the other side of the switch goes to the tranny. Thus, the only way the over drive can be activated is when you turn the switch on.

If I remember the underside of my car correctly, this wire doesn't exist... on all years but 86, there are three wires. On 86, there are two. From what I can tell from the service manual, there's a pressure switch wire and a temp sensor wire. That's it.
[RICHR]

 

[corvette66]

I'll have to get under there tomorrow, since i have mine all taken apart it should be easy to see everything. There should be a spedometer cable or switch there too somewhere.