I've read about the CCC (Computer Command Control or something) that GM put in the 1981 Corvettes and I'm curious of what it does. I'm going to look at an '81 (yeah, another potentional...) with 43,300 miles, all the options, and it is an automatic for 10,000. I just would like to know what the CCC did and controlled. My dad is not a fan of electronics/computers in cars as it makes it hard for him to tear it apart and rebuild it the right way and he is my automotive guide. So, what have you guys got for me on info on this thing? I suspect it doesn't do much, but I could be, and often am wrong. Thanks guys, maybe I'll buy this one :) :cheers:

 

I believe it metered the carburetor inputs. It may be a very simple system indeed.

 

Computer Command Control is correct, the air/fuel mixture, timing advance, and Torque Convertor lock-up are controlled by it, there are other things, but those are the biggest.

 

The ECU (computer/confuser) monitors various things but just controls the spark timing, the torque converter lockup function & the mixture control on the primaries.
It's a fairly simple system (once you've sussed it all out) & an awful lot of people don't like it. If you want to mod the car for max. power then the computer becomes a brick wall in that it relies on manifold vacuum for determining the fuel mixture - & manifold vacuum drops when using nice cams with lots of overlap. If you're not after huge amounts of power then the system can be your friend(!). It gives good fuel economy, also emissions (if that's a problem) & has a basic diagnostic feature that points you in the direction of any problems. Most problems I've had have been due to previous owner "modifications" to it & dirty connections (usual electrical system faults). The good thing was that the ECU pointed me at the circuits with the bad connections, making finding them a lot easier. Additionally, somebody had made a real lash-up of re-routing vacuum hoses which caused a minor air leak (EGR solenoid open to the atmosphere). If it hadn't of been for the Check Engine light occasionally flashing at me, I would probably never even been aware of a problem.
Various Vette "experts" told me to sell the car, throw the ECU, stick a Holley on it, it will never run well, etc after I got it, but it runs fine & was giving fuel economy in the low 20's - b4 the locking torque converter packed up :(
I like the '81 - composite spring, alloy x-member, good airflow to rad, etc, etc, & wouldn't let having a ECU in the system put me off buying a good 'un. If it all becomes too much to cope with, then taking the ECU off isn't a big deal.
Good luck with whatever you decide!
:cheers:

 

I have an 81 where all that STUFF has been removed and it runs great. I just hate all those dangling wires in the engine compartment and while I'm rebuilding the engine and front end I'm going to try to get rid of as many as I can to clean up the looks. I do still have the cable going to the trany that I suppose controls the lock-up TC. Since it is not hooked up does this mean the TC has been changed? Or will it function without the CCC. What mods do I need to do to the trany when I rebuild it to overcome the missing CCC. Any help would be appreciated.

YBnormal..drive a Vette

 

UKPaul has it right. If you want a cruiser then the system is just fine. If you want to modify it for lots of power and stay emmisions legal then you should look for a different year. It can be done, but you need to understand the system. I am waiting for my state to decide what it is going to do with emmision so I can decide how to modify mine. My current thinking is I am going to take the challenge to modify it, and keep it legal :cheers:

 

Ybnormal,
If you've got a TH350C there should be an electrical connector on the d.side for the lockup function. There are 4 pins on it. The standard harness going to this connector only has 3 wires in it (labelled A, B & C at the top connector on the firewall & A, C & D on the g/box: B goes to D - great init?!). Having just looked inside my trans (MX2), pin C doesn't connect to anything. Pins A & D go to the solenoid (via a pressure switch wired in series). The computer just switches current through pins A & D in the g/box when lockup is required.
The current is switched through the solenoid via a relay on the firewall. 12V is present at the relay (if the brake is off) & the ECU earths this 12V when it wants lockup. This throws the relay to send 12V (from the fusebox) to the solenoid via the pressure switch.
So you just need a switch to connect 12V (fused!) to pin A & run a wire from pin D to earth.
If you need a pic of it all send me an IM & I can email it to you.
:cheers:

 

So it isn't that big of a deal? This winter my dad and I will be building some engines. Either a couple of blown small blocks, or NA small blocks for our Corvettes. Once the engine is out it'll probably be pretty easy to get rid of the computer and wiring.

If I get rid of the computer, will my transmission still function without trouble?

 

Yes..... if you hook up some sort of switch to lock the converter. You can run OK without locking it, but locking gives far better fuel economy. You can use a manual switch mounted somewhere or I think you can get vacuum operated ones as well.
:cheers:

 

If you take out the computer, you need a new carb and distributor.
79 didn't have the computers... maybe a better choice (closer
to rest of C3 line for alternate parts...

I've been through Eau Claire several times - have fun.

 

UKPaul,
I have disconnected the computer in my 1981 Vette and tossed it. I would like to know more about how to install a manual switch to the trans lock in/out converter?????? :confused:

 

Delta,
I can email you a wiring diagram for the TCC lockup stuff if you IM me your address. It's nothing special (I'm no artist!) but it's easier to read than the manual & may make the following ramblings a bit clearer :)
The computer works by earthing a circuit which comprises a fused 12v supply going to the EGR/TCC relay via the brake pedal switch (brake on, then no 12v to the relay, thus unlocking the converter). When the ECU decides to lockup (which I think is a decision just based on coolant temp), it earths this 12v. This throws the relay contacts which routes another fused 12v supply through the g/box solenoid to lock up the TCC. There is a pressure switch (some sort of switch, anyway) wired in series with the solenoid in mine (MX2) which I assume ensures no lockup in low gear. I'm pretty sure that all the computer does is supply voltage to the solenoid once the engine is up to temp.
So there's a choice. You can:
1) Put the switch in the part of the circuit that the ECU controlled (if you've still got the EGR/TCC relay wired in). This is a black/tan wire. There should also be a TCC test connector under the d.side console cover which you could switch to earth instead (might be easier as it's near the dash). This would probably be the best solution as you'll still have the brake switch functioning & the high current is switched via a relay & not your switch (mine passes a high current, but maybe that's because the solenoid is burnt out?).
2) You can put the switch directly in the circuit to the solenoid. If you follow the wires up from the g/box case connector there should be another connector between the rear of the d.side valve cover & the firewall. There should be 3 wires in this 4 pin connector, labelled A, B & C. C goes to the g/box connector but in my MX2 it doesn't go anywhere inside (that I could see). Pin B at the top connector goes to pin D at the g/box connector. There should be 12v present at pin A of the top connector & pin B goes to the EGR/TCC relay via that mass of wires cluttering up the firewall. If you run the wire from pin B to your switch & then earth the other side of the switch, you should be able to manually stick 12V through the g/box solenoid to lock the converter. Earthing the wire at pin B (D on the g/box connector!) is a good test to check that the g/box internals & solenoid function OK (as long as 12v is present at pin A). Mine doesn't :(

I've seen vacuum switches mentioned b4 but haven't looked at them at all as I'm trying to just get mine to work however I can!
I hope all the above is correct. I took the info from the '81 wiring diagram & buzzed it all through on the car & checked out the colour coding as far as I could. The diagram ties up with my cars actual wiring so I'm pretty confident that it's correct. It seems that the main function of the ECU in the system is to just decide that the coolant is hot enough! The brake pedal switch cuts the power to the ECU circuit & the switch in the g/box seems to be for preventing lockup in low gear (does low gear = low oil pressure? I dunno, auto boxes are black majic to me ;) ).
Personally, having seen the size of the spark when I ran current direct to the solenoid, I'd put the switch in the circuit the ECU was in & let the relay handle the current, rather than your switch.
Hope some of this made sense!
:cheers:

 

UKPaul,
E-mail is gmwl@hawaii.rr.com
I'm very confused by the instructions provided in your return reply....hope I'll be able to better understand the system in your E-mail. I've ripped out the entire wiring system including the ECU.....I would like to wire in a switch to lock and unlock manually at my discreation....Thanks for all the info.... :confused:

 

Hmmm.... sorry about that. I was having a particularly bad day at work & just started rambling :lol: A short, concise email is on it's way!
:cheers:

 

Hey UKPaul would you be so kind as to e-mail me that short concise email too please. ( jackback4@comcast.net ) I need to check mine out too and thanx. :cheers:


[Modified by Armstrong, 5:04 AM 5/17/2002]

 

Done! Some bits (what you want) are concise, but I've also tried to explain what's going on, just so you know how it works ;)
Meanwhile, if anybody knows anything about how the tranny side of the lockup works, I'd love to know. All ECU & TCC/EGR relay diagnostic tests in the manual result in "Problem is internal". Excellent! :( Now what do I do?
:cheers:

 

Finally found somebody who knows about the TH350C. If power is passed through the solenoid but the torque converter doesn't lock up then, next time you take the tranny pan off, check the solenoid. If you pass battery voltage through it there should be an audible "click". If not, the solenoid is the problem. If there is a "click" then the problem will more than likely be the pressure switch that's wired in series with it, or the Governor valve body (or some other name like that). But most times, if the Governor valve(?) goes wrong it locks the converter, which will be obvious as it causes stalling when you put it into gear.
The pressure switch is there to prevent lockup in low gear & to also unlock the converter when you decelerate(sp?).
It's simple once you know what it's supposed to do!
:cheers:

 

ok thnaks now that I know where the check engine light is on tha 81 vette does it come out from the front or do I have to get behind it some how? Thanks for responding to me for the location..

 

If this is duplicate info, ignore it...I didn't see a thread with all correct info.

The '81 computer system: reads the O2 sensor in the exhaust system; it controls spark timing; it sends input to the carb so that it can properly regulate the air/fuel mixture via the fuel metering solenoid in that 'one-year-only' carb; it manages the lockup function on the automatic transmission; it operates the OBD-I diagnostic system to aid with engine malfunction repairs; it also 'reads' info from other engine sensors so that timing and fuel mixture info is accurate.

So, it is really pretty dumb...just like the new ones.

If you don't want to replace the carb, distributor, and substitute a tranny lockup controller for the one in the computer you have, just leave it all alone (assuming that it still works OK).

 

I just had all my smog stuff removed, new Edelbrock carb, Edel EPS intake and Accel HEI.
I must say it runs 100 times better.
also added Comp Cam.
Make sure if you do use a heat separator gasket to keep from boiling your gas and get a lower thermostat to reduce temps under the hood.
I am still struggling with the Edel carb, great 1/2 to full throttle response but hesitates on light footed cruising and I'm still only getting 10 MPG so the quest goes on.