700r4 torque converter lockup

[skysoldier173rd]

I'm using a 86 GMC as a donor vehicle for the 305 and overdrive trans 700r4. I have been told the vacumn/electrical switch for the converter lockup is located on the firewall of the truck. Well, there are several things on the firewall with vacumn lines and wires, and I don't know which one is it. Obviously, i want to move it when the motor and trans come out, so i want to be sure i have the proper item. Does anyone have a picture of the switch?

[Oklahoma]

in my opinion dont waist your time, I did the lock up deal on mine, and at 75 I flip the switch and it only drops it about 100 rpm's, not worth it.

[vin63]

It might be easier to get a toggle TCC lock up switch harness conversion. That's what I usually do for the 700R4 conversions.

[raycow]

I agree with vin63. A manual switch would be friendlier than the vacuum switch. But you don't need an overpriced kit from one of the aftermarket vendors. Just use a toggle switch from a hardware or home supply store.

Definitely make sure you hook up the converter clutch one way or another, though. It isn't just the 100 rpm. The converter puts a lot of heat into the transmission oil when you let it slip continuously.

Ray

[skysoldier173rd]

So, if i go with a simple switch all i need is 12 volts sent down to the solenoid inside the converter and it will lock up. I'd rather have the control over it anyway than the automatic lockup. Also, I'm wondering how would you kick it down other than the switch, or would that be the only way to disengage it.

[fleetsidelarry]

Originally Posted by skysoldier173rd

So, if i go with a simple switch all i need is 12 volts sent down to the solenoid inside the converter and it will lock up. I'd rather have the control over it anyway than the automatic lockup. Also, I'm wondering how would you kick it down other than the switch, or would that be the only way to disengage it.

depends on whether you mean "kick down" to 3rd from 4th (OD) or "disengage". Kicking down is handled differently by your transmission. Mine is set up as a manual lockup and only in 4th, I don't have to disengage it when coming to a stop, for instance, because, as the transmission automatically downshifts out of 4th the lockup no longer is working. The advantage of the vacuum switch is that is disengages the lockup when you accelerate. I really don't use my lockup very often, only when trying loaf along with interstate traffic at 75 or so. Like the guys said before, you do not have to spend big bucks to do this. I also get more of an RPM drop than Oklahoma does, maybe 200-250.

[skysoldier173rd]

So Larry, my transmission will automatically shift out of OD back to 3rd when i hit the brakes even though the switch is still on?

[fleetsidelarry]

Originally Posted by skysoldier173rd

So Larry, my transmission will automatically shift out of OD back to 3rd when i hit the brakes even though the switch is still on?

Yes, the converter lockup is a separate function from downshifting AND lockup is different than OD. OD is 4th gear, separate animal from the converter. Think of it as 4th gear (OD) + lockup, 4th - lockup (switch off) is just 4th gear.

I put a kit in mine, I believe it was from TCI, where one of the pressure switches is swapped out and a minor bit of rewiring done internally (pan off), I can't remember exactly, I'll have to look it up BUT I have subsequently read that you don't have to swap out the switch. I think Captainfab does just a simple switch arrangement. Someone talked about it recently on this forum. Here's one link I have about doing it yourself with a pressure switch and a vacuum switch:

http://www.73-87.com/7387garage/drivetrain/lockup.htm

here's one with a simple on-off switch:

http://smokemup.com/tech/700r4.php

[fleetsidelarry]

I said: "I think Captainfab does just a simple switch arrangement." My bad, it was Txfirefighter whose diagram was referenced in a previous tread. The straight switch arrangement MAY lockup in 3rd also, and 2nd can apparently be done, also. I think if mine locked up in anything but 4th I'd want some sort of auto-disengage.

[Russ65C10]

I used the adjustable B&M lockup kit, its around $180 works great.


http://www.streetperformance.com/m/c...-m-racing.html

[low79fx]

Not to hi jack this tread ,but can someone elaborate on whether it is actually necessary to hookup power to lock up converter.Or can it be ran with out any juice going to it as if not even being there i.e non lockup TH350.What I am getting at is I am going to install a TH350C which has a lock up converter but I am not going to hook power to converter yet.Can I run it with no issues as described?

[raycow]

Originally Posted by low79fx

What I am getting at is I am going to install a TH350C which has a lock up converter but I am not going to hook power to converter yet.Can I run it with no issues as described?

Yes, you can certainly run the transmission without power connected to engage the converter clutch. The unanswered question would be about the long-term effect on the tranmission. You would be putting more heat into the transmission oil (from converter slippage) than the oil cooling system was designed to handle.

[skysoldier173rd]

Thanks larry, think i'll go with the manual switch on the dash and retain control. I tow alot with my F250 diesel and it has that manual dash switch, only way to go while towing and i don't want lugging in the low to mid ranges when it's so much easier on the motor/trans to cruise in lower gear.

[skysoldier173rd]

pulled the donor vehicle engine/trans together. everything intact along with carb and vacumn converter lockup switch. the tv cable, electrical plug not disturbed whatsoever. therefore i'm thinking all i will need to do is add 12volts off the key and plug in the vacumn line and the trans should totally function as it did in the donor vehicle including the converter lockup and unlocking. anyone disagree?


www.picturetrail.com/skysoldier173rd

[raycow]

Originally Posted by skysoldier173rd

therefore i'm thinking all i will need to do is add 12volts off the key and plug in the vacumn line and the trans should totally function as it did in the donor vehicle including the converter lockup and unlocking. anyone disagree?

Well almost. You would need to wire the brake switch in series too if you wanted it to behave as if it were completely stock. But you don't need to take off the pan and fiddle with the internal bits, like too many people want you to do. It's just plain not necessary.

Ray

[skysoldier173rd]

someone on here said that when it downshifts to 3rd, it will automatically unlock the converter. Is that true? If so, don't need to do that. I did notice another double set of wires coming off the tranny wires harness hanging lose. wonder if that is the brake wires
If i do need to do this to the brakelights, does anyone know which wire would to the brakelights?

[skysoldier173rd]

..

[raycow]

Originally Posted by skysoldier173rd

someone on here said that when it downshifts to 3rd, it will automatically unlock the converter. Is that true? If so, don't need to do that. I did notice another double set of wires coming off the tranny wires harness hanging lose. wonder if that is the brake wires
If i do need to do this to the brakelights, does anyone know which wire would to the brakelights?

That's not how the stock setup works. Most of these transmissions will normally lock up in 2nd, 3rd, and 4th. That's why the brake switch is a good idea. Without it, the 2-1 downshift can be rather harsh as you come to a stop. Btw, you don't connect anything to the brake lights. The brake switch has two sets of contacts, and you use the set that is closed when the pedal is up. It is just a straight series circuit. The power has to go through the switch before it gets to the transmission.

If you don't like it this way, you can wire the transmission to lock in 4th gear only, provided it has a 4th gear switch installed. Now you get to take off the pan, because you have to see what is hooked up on the inside of the 4 prong connector. There is no way to tell from the outside, because the switch will be open except when the transmission is in 4th gear.

There is one other possibility you can check out that might save having to pull the pan. Look at the end of the harness that has the transmission connector. How many wires are there at that end? The number of wires, not the number of contacts.

Ray

[skysoldier173rd]

sounds like the switch is the best option. just need to figure which wire goes to the converter solenoid. I'll look through some old threads here unless someone out there can help. I have isolated the switch now, so just need to know which wire to install the switch.

[raycow]

Originally Posted by skysoldier173rd

sounds like the switch is the best option. just need to figure which wire goes to the converter solenoid. I'll look through some old threads here unless someone out there can help. I have isolated the switch now, so just need to know which wire to install the switch.

You need to do some circuit tracing first. Which switch are you talking about? How many wires go to the transmission connector? Also, do you have a multimeter or some kind of continuity tester?

Ray

[skysoldier173rd]

there are 3 wires, white,green and blue. I was refering to the vacumn switch on the other end of the wires that operates the converter solenoid. wouldn't you basically replace that with a toggle switch?

[raycow]

Originally Posted by skysoldier173rd

there are 3 wires, white,green and blue. I was refering to the vacumn switch on the other end of the wires that operates the converter solenoid. wouldn't you basically replace that with a toggle switch?

Yes, you can replace the vacuum switch with a toggle switch and that will give you full manual control. If you aren't going to use a brake switch, connect the two brake switch wires together. Lastly, if you have 3 wires going to the transmission, the other end of one of them has to be grounded. The problem is, I don't have a wiring diagram, so I don't know which color wire it is.

You can check out the wiring before you install the transmission in the car. When you get it right, you will be able to hear the solenoid click.

Ray

[skysoldier173rd]

sounds like that's what I really need. Probably should fuse the hot wire with an in line maybe? I'll search this forum and see if i can find some diagrams for wiring the switch and also the ground. Thanks for your help.


www.picturetrail.com/skysoldier173rd

[raycow]

Good news, for a change. I was looking at this diagram on a totally unrelated thread, and it just happens to show the internal wiring for the transmission connector.
http://chevythunder.com/16136965_ecm_diagram.htm

According the diagram, the TCC solenoid is connected across A & D with A being the (+) side (the solenoid IS polarity sensitive), so connect power to A and ground to D. The 4th gear switch is connected across B and an internal ground, so if you want the converter to lock in 4th gear only, just put a jumper across B & D and don't use a ground wire.

Disregard the wiring that goes to the ECM, because it doesn't apply in your situation.

Ray

[skysoldier173rd]

Best news I've heard lately. Something about this build needs to be easy. This was supposed to be an easy bolt in, but it's fought all the way. Put a 413 in a 41 coupe once, don't think it was any harder than this.

Thanks Again