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700R4 Lockup questions.

Codeman96

Codeman96

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I have been doing some searching on here and I think I may have found a problem with my 700R4. I never hooked up the vacume switch when I changed motors and went with a Edelbrock intake and carb. I have never felt that my TV cable was right anyway so I am going back to my Q-jet also (for other reasons besides that).

What do I need to do so that my converter will only lock up in OD? I know there is a kit available but I have also have seen where people have accomplished this on their own.

What does the plug look like? I have a pic I will post when I get home of the one that I had left over :rolleyes: when I did the swap. Can you guys help me or refer me to a site that has good info.
 
Lots of sites about the 700 and lockup/tv/etc., but the TCC plug is a 4 prong weatherpack, white from all I've seen.

ONLY locking up in OD would require some wiring changes of course. Any reason you would not want it to lock in 3rd?
 
Well not necissarily. But I would like some control over it. I know that right now when pulling my camper (3500lbs or so) in the hills that it pulls it down bad in 3rd gear. Going to the race track on flat ground with the race car in tow it rolls on with out problems. I had never thought about the converter not unlocking but it makes sense. The motor I have put together shouldn't have that much trouble pulling a grade with that kind of weight on it. I am sure that the 3.55s aren't the greatsest but it shouldn't be that bad with 31" tires. I like the idea of being able to turn the lockup off when I want to. I know that plug has been left hanging somewhere so the convereter will lock up and stay that way right? Would putting the vacume switch on my current motor be a better idea or making it selectable the best? I am a little lost to say the least and I am really curious to see if this is what is hurting my performance pulling a trailer.

I am open to any ideas. Have I screwed up somewhere else possibly?

Thanks for the help in advance.
 
I'd put the vacuum switch back in, see what you think. Every little bit helps when towing, and it's hard on the converter to stay locked up under a heavy load.

I'm not sure what kind of vacuum those switches work at, but since vacuum drops off so rapidly with throttle, I doubt you'd notice it locking up at anything other than cruise. It should unlock in any gear with that switch in place, so whether 3rd or 4th is unimportant, just that the converter unlockes when you have a high load on the engine.

I was very pleased with the stock setup on mine. I don't like adding a bunch of switches and wiring when what is there is automatic (get a manual if you want to control things hehe) in the first place, and works great, at least IMO.

If you go to a wrecking yard for these pieces, that plug should be pretty easy to find, I'm sure things like the Astro's, S10's, etc used the exact same connector, although wiring could vary a bit. The vacuum switch from my understanding is a non-ECM application only, so full size trucks and vans. For the C/K trucks, vacuum switch donors should be all 700R4 trucks '82-86 without california emissions. (that used the computer controlled carburetion setup)
 
go to www.700r4.com

they have a diagram of the 4 wire harness, easy to splice into and make your truck lock/unlock when you want.

BTW where is the vaccum switch? never been able to locate one,i think mine is unhooked
 
I should have everything. My old motor is complete and sitting over at my old shop in the floor. All of that stuff is still attached. Anyone got a pic of the vacume switch? Any idea of how it gets plumbed in? My motor is built for torque so pulling plenty of vac shouldn't be a problem. I also have a B&M shift improver kit that I am going to install to firm up the shifts. Keep in mind mine is an '84 so I don't know if all of the plugs looked the same.
 
I can't really describe the switch, don't have one here, but it's a simple one hose hookup, barbed plastic IIRC.
 
Well I don't know what happened posted the pic of what plug I found but it disappeared??? Anyway I don't remember any weather pack plugs on my '84 and this is the one I did find hanging.Could this be it?
11139Dsc00302.jpg
 
And here is the switch I found. This about all it could be after I look at the rest of what was left on th old motor. Next question manifold or ported vacume?

11139Dsc00303.jpg
 
Your last pic appears to be the EGR solenoid, does that red plug fit it? (thats a weatherpack connector BTW)

The vacuum switch IIRC is also "disk shaped". You'd want manifold vacuum for the TCC switch.
 
Ok, there are really two vacuum switches. What you have in those pictures does not control lockup. It is an electrically controlled vacuum switch. It controls flow of vacuum to the EGR when the torque converter is locked up. This switch is typically located at the rear of the passenger side valve cover. (Hint: this is a great place to tie in and get feedback back from the transmission to see if it is locked or not)

The other switch (that was referred to earlier in this thread) is a vacuum controlled electrical switch. When the engine vacuum drops, it breaks the circuit to the tranny and unlocks the converter. That switch is typically located on the firewall near the brake booster.



If all you want is a manual override to prevent lockup, there is a switch mounted under the dash on the brake pedal assembly. That thing opens whenever you push the brake pedal, to ensure that the TCC is unlocked while you are braking. A switch in series with that kills all lockup without running any wires through the firewall.

If you want to lock only in 4th, usually that can still be done without opening the tranny, assuming you have 3 wires going into your transmission. There are a lot of variations of internal wiring, though.
 
I thought it was mounted on the other side of the firewall. I believe if you move the stuff on the other side of that switch, you will see a vacuum line connected. Pretty sure I can see that there. That little nipple likely doesn't take a vacuum line.

Did you find the TCC plug near the tranny?
 
Going home shortly and I am going to trace the wires up into the engine compartment. I think I might actually have time this evening. LOL
 
Ha! I found it! My last pic is the switch and yes there was a vacume line connected to it...... But the other end had rotted off and was laying down in the fenderwell. LOL I cut off the end and plugged it into the vac tree so after the wife gets home and corrals the kiddo (it ain't worth putting her back in the truck LOL) I'll give it a try and see how it does. After reading what I have this has got to help some of my problem. I am still thinking of putting it on a switch.
 
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