What needs to stay?

[MylilBowTie]

I have an 86 C20 with the 700r4 transmission. What do I need to keep for the lockup to work properly? I am removing the knocking 305 to replace with a 350. In doing that I want to clean up the wires and remove the emissions mess. I'm removing all the associated ESC parts - computer, knock sensor, wires. Pollution air pump, lines and hose. Installing hooker headers and may install an Edelbrock 1406 carb. If not it will be a stock Q-jet non feed back carb.

[heavychevy79]

I think the speed sensor going to the back of the speedometer is all you need,
plus power to the computer, but it may need the throttle position sensor
thats in the CCCarb.
I think you could rig it with a switch on the dash, but it would stall the engine
if you stopped with it turned on.

[pig rig]

being a 3/4T your trans may be a 80le or 60le if you pull the tbi and all the sensores besides a carb you'll need a converter lock up kit for the trans to shift and I belive you'll need a distributer because the ecm controls the advance and with no sensors the ecm has no idea what to do

[heavychevy79]

Originally Posted by pig rig

being a 3/4T your trans may be a 80le or 60le if you pull the tbi and all the sensores besides a carb you'll need a converter lock up kit for the trans to shift and I belive you'll need a distributer because the ecm controls the advance and with no sensors the ecm has no idea what to do

Yea if the dizzy doesn't have a vacuum advance and weights he will need to change it. Some computer cont dist still have vac advance and weights, and they work fine with out the computer hooked to it.

The 4L80 came in 91 if I remember right.

[MylilBowTie]

Its not a tbi engine that was for the 87 model year. The Transmission doesn't have a computer per say as far as I know. I know there is a brake switch, and a few vacuum switch's.

It would be sweet to have a 4L80E but those are pricey and the transmission controller as well.

Just want to get this other 700r4 working properly. So that it will lockup when it needs and not fail sooner than need be.

The original 700r4 was junk when I got the truck. I replaced it with a th350 9in. Now I want to get OD for it again.

The feed back carb is only for the cold startup. It will add more fuel to help it transition better to warm up.

[MylilBowTie]

The 700r4 is now being called the 4L60 and the 94 and up electronic controlled one is 4L60E. Same with the th400 now being called 4L80 and the electronic controlled one a 4L80E.

[Damien]

The th400 is a 3l80. You will most likely need a vacuum advance dist. I'm not really clear on how the TC is locked in stock form. I know there is a vacuum switch on the intake that will activate the TCC solinoid. It may or may not used the comp. You will need a TV cable and have it hooked up and adjusted correctly or your new 700r4 will become junk very fast. I should go look this up on Alldata. If I find anything I'll get back to you.

[Damien]

here is a wiring diagram. The TCC and dist. are run by the PCM. It looks like you are going to need a kit from TCI or painless.

[MylilBowTie]

Is that one for a California emissions truck? My truck doesn't have an ECM. Just the one that is for the ESC to retard the timing if detonation is detected by the knock sensor.

[Damien]

I don't think it gave me the option. I was under the impression all vehicles with feed back carbs had an ECM. The Ecm is mounted behind the glove box to the underside of the dash.

[MylilBowTie]

The carb had temp sending units connected to it to operate. They are used on 85-86 year trucks. 87 was the switch over to TBI and full ECM engine control.

Looked at the TCI TCC switch. Its kind of spendy especially when I already have the stock parts to operate it. Guess I need to start tracing the wires and see where they go.

[heavychevy79]

The torque converter does not need to lock up for the rest of the transmission to function properly.