700r4 lock-up

[Matt69olds]

I know far more about the transmissions than I do about the specific engine control systems of these trucks.

I knew the early 80s had a special ignition module (ESC) that had a different method of timing control. The later years used a ECM controlled the carb, ignition timing, and the lockup converter. The ECM also controlled some emissions control solenoids and lots of other things. I think the ECM is behind the glove box.

 

[BJedi76]

I am assuming there is only one or the other, not both.

How do I verify which one I have?

I thought I had an ECS.

Can it be told by the wire colors or do I have to look at the device itself behind the glove box?

 

[Turbo4whl]

Reading through this, it seems you have the vacuum tip-in switch on the firewall? If this is the case, that is what controlled the lockup. The brake switch is just a defeat to turn the lockup off. Do you just need the new trans wire plug?

When I swapped out the T350C I needed to change the plug for the 700R4. Is the rest of the harness still there?

 

[yepyep]

I know far more about the transmissions than I do about the specific engine control systems of these trucks.

I knew the early 80s had a special ignition module (ESC) that had a different method of timing control. The later years used a ECM controlled the carb, ignition timing, and the lockup converter. The ECM also controlled some emissions control solenoids and lots of other things. I think the ECM is behind the glove box.

i could be wrong but i belive only the 87s with tbi fuel injecjtion had ecms i have two trucks a v10 and a v20 both have an ecm behind the glove box Vseries was only made for 1987 then the style changed but they are identical to k series trucks just fuel injection

 

[BJedi76]

Yes, i need the 4pin vacuum switch wire.

none of the local auto parts stores can find it.

What is its technical name or some kind of reference number?

I also feel like I should replace the brake switch, Or at least have a spare on hand.

 

[Turbo4whl]

This connector?

You must be registered for see images attach

The 700R4 only uses 3 of the 4 pins. The difference between the 700R4 and the T350C (2 pin) is you need to add a ground wire to one of the pins.

There are several on Ebay....


https://www.ebay.com/itm/284293303087?epid=1539454765&_trkparms=ispr%3D1&hash=item4231338b2f:g:gxoAAOSwJodfjJJo&amdata=enc%3AAQAFAAACgBaobrjLl8XobRIiIML1V4Imu%252Fn%252BzU5L90Z278x5ickk7PdDazAlGltMLJlUhrWsD6q7orYKlPRmYKSj5Li9Q517ZG7lRUwJaavZJibq3E1%252Fh%252Fp9DI%252FrdLEmk0bWNgoEQotVM0ryOYEMUdhTbsoBwmljjy4jjWlhOFAZUz6KnUC0W4hQKvufSiN0A8x1PjwUtKgQTjZlI2VZOp1GyNEMyZ3Nbevfdw47hU6Qi2F%252FccNOq13TgVYCcR9H%252FpOqahC8%252BY7CvHzxi5WJ1%252B2t6Fl3b%252F9Xnif7tltKktdF2Klzbu6RFuUP4uVBNxTPsUvoRKE%252FVwTHV%252BRrjVZHXSpiKt8jmZwTR8kIVcxK35BttMGOkOBIIUD0csOBtxlOC0Ybncv6SWs8CvZ8HvDEjB6DnS1vyD7iRKr9fXpjrLfHd5Fp8%252F8AG0ZNZIbRDeVxY3aNBFykiPQnCowg4dr0Liq9zEk1wy%252FTpL2k2%252FM3%252BycBjbXbyoBGkVL6OERGstpH1F67BGXnJ4aZAeAjZkDv%252B%252BpgrwVqRqLgvL4sJDHamxMCzXbni4GkPUpKegiBZAtFXuCENiZqN6408V5Lc12I2YB3FMjYgNG9Dr0YcSDz99U8fsGriPbnOiqgIVzU%252Bxaub6qYf%252BDU%252BXJcOl5NSeuL%252FdzLuLSOithv7EqQBnoZ8%252B1oiegOlGx0qhCmwDFlt0no1hqAalzbLRJR%252FmpMMA%252Bpw%252FA1%252Fk61EikB29cRdcjb%252FaErazFvyNfuotCC66FLwWshoiNBIvPXjE03Z5v2bnSo0kQzXv4lBWN0%252Fb%252FSVKUCEeBl1euH1CUFUk2g8p3w%252FM4qwNQOIQtx3FJcfJeIgq76ZbxrhZ%252Fy3HQ%253D%7Ccksum%3A284293303087ebf50c7ade44473e9c2b011b4ccb8f1e
%7Campid%3APL_CLK%7Cclp%3A2334524


https://www.ebay.com/itm/222760618481?epid=2084916987&hash=item33dd9149f1:g:P7UAAOxyf2pR5XrB

 

[BJedi76]

So, apparently, I need two connectors, and then wire them together.

now that I know what it’s called, it appears that no one sells the patch cord with a plug at each end.

So I need to find the vacuum switch end connector.

then, i guess, just wire the pigtail ends together?

 

[Turbo4whl]

Should be able to find the whole harness at a wrecking yard. Truck with the trans removed probably has the complete harness minus the 4 pin connector because it was cut off during trans removal.

The harness has wires to the brake defeat switch and the firewall vacuum switch. One more to power feed.

Aftermarket sells a complete kit with an aftermarket adjustable vacuum switch too.

https://www.ebay.com/itm/283673327508?epid=251985331&hash=item420c3f7794:g:JT4AAOSw5~ldyttu

 

[Ricko1966]

I think what everyone is not thinking about is all 700r4s are not wired the same or even have all the same components inside. Not all trucks control TCCC lock up the same. And Bejedi76 it's not as simple as buying a couple of pigtails and boom every thing works. I didn't look at the kit turbo4wheeler put up but that is probably your easiest solution.

 

[Ricko1966]

So, apparently, I need two connectors, and then wire them together.

now that I know what it’s called, it appears that no one sells the patch cord with a plug at each end.

So I need to find the vacuum switch end connector.

then, i guess, just wire the pigtail ends together?

No it's much more complicated. You need fused power through the brake light switch, to the vacuum tip in switch,to the transmission then 1 of the 4 pin leads will need to ground to the transmission case.Inside the transmission pan the TCCC will have to have at minimum 12v from the 4pin connector and a ground through the 4th gear switch.

 

[AuroraGirl]

Not having the converter unlock when under hard throttle would be a pain. My K-10 had 3.08:1 gears and would be a total dog if converter was permanently locked in 3rd and 4th. I wired mine up so I can lock it whenever I want, I can keep it unlocked whenever I want, or I can let mother GM control it through vacuum and brake switch like she intended. Makes me happy to have control.

I personally would not want it to go straight to lock up and be locked unless a drop to 2nd occurs
Ben.

Can... it even shift when locked? I feel like it’s gonna be a pretty jarring shift if it does

 

[Itali83]

Can... it even shift when locked? I feel like it’s gonna be a pretty jarring shift if it does

everything factory and working properly it already shifts from 3-4 with the converter locked with no problems. With a shift kit it’s a little harsh but no big deal.

ben

 

[AuroraGirl]

everything factory and working properly it already shifts from 3-4 with the converter locked with no problems. With a shift kit it’s a little harsh but no big deal.

ben

Must be how he forward gears apply
Like my car can’t go into 4th if it’s locked in 1st or reverse... may be wrong but it’s something that works to that affect. It’s not something it would often do but meh

 

[Ricko1966]

Must be how he forward gears apply
Like my car can’t go into 4th if it’s locked in 1st or reverse... may be wrong but it’s something that works to that affect. It’s not something it would often do but meh

Yea. My car won't go into 4th if I'm in reverse either, weird huh?

 

[AuroraGirl]

Yea. My car won't go into 4th if I'm in reverse either, weird huh?

FROM. It was an example calm yourself