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Old 03-04-2013, 10:37 PM   #1
Doug_J
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700r4 rewire help!!!

Okay I have a 1985 Chevy 305/700r4 2wd that has the Cali. smog crap with the ESC distributor. I have removed all the smog and replaced the carb and distributor, now my problem is the 700r4 was tied into the ESC/smog computer crap an I had to cut the wires. So now I need to know how to rewire the 700r4 to work and I do not have the vacuum control that everyone talks about assuming because it was tied into the computer. I have been looking at this

http://www.73-87chevytrucks.com/tech...rol_wiring.jpg

But that has made my head hurt more than help. That comes from this,

http://forum.73-87chevytrucks.com/sm...0pcnhos8t549g4

I have looked all over the web but cannot find a lot of info on people that have ran into this issue or have pictures, so any help would be much appreciated.
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Old 03-05-2013, 01:40 AM   #2
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Re: 700r4 rewire help!!!

its the converter lock up if you wont you can wire in a switch and turn it on when your on the highway or you can get a lock up control
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Old 03-05-2013, 02:34 AM   #3
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Re: 700r4 rewire help!!!

well see thats what im trying to figure out is how to wire it up to work without the computer and me having to do it manually. I have one wire that goes into the firewall on the driverside and then the three wires right behind the distributor I cut, so im really trying to figure out what each wire does and do I need to go take the vacuum controller off a salvaged truck?
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Old 03-05-2013, 02:41 AM   #4
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Re: 700r4 rewire help!!!

Quote:
Originally Posted by spencer_41188 View Post
its the converter lock up if you wont you can wire in a switch and turn it on when your on the highway or you can get a lock up control
I dont know if I'm an idiot or I should just look at this when im a little less tired but maybe you can explain this diagram to me?
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Old 03-05-2013, 04:09 AM   #5
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Re: 700r4 rewire help!!!

maybe that was a bad diagram but heres a better one

this one if from http://www.jaguarhunter.org.au/Techn...00_gearboc.htm there retrofitting a 700r4 in a jaguar but it has a parts list and a diagram to make your owne manual lock up controller
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Old 03-05-2013, 08:37 AM   #6
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Re: 700r4 rewire help!!!

Your head hurts cause its all incorrect. The ECM only controls timing. Wires go directly to distributor. Timing does control engine vacuum. Engine vacuum does control lock up. There are two vacuum switches. Passengerside is ECM wiring. Driverside is for converter lock up. Here is a standard lockup wiring example for our trucks.
http://www.73-87.com/7387garage/drivetrain/lockup.htm
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Old 03-05-2013, 01:48 PM   #7
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Re: 700r4 rewire help!!!

Well see after everything I read online I thought the 700r4 didnt go to the computer either, so i got to tearing out the cali smog crap but the wires did run into that along with a vacuum hose. Theirs nothing on the driverside near the break booster, now their is somthing on the passanger side that takes 3 wires and a vacuum hose that also went into the computer, they called it a vacuum sensor on that wiring diagram. So basicly I know for a fact that it went into the computer, now that vaccum sensor on the passanger side, can it be used to hook up the 700r4 maybe? Is their anyway way for me to wire it up without having to pull that pan? I mean I assume their has to be being my truck came with the 700r4.
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Old 03-06-2013, 12:47 AM   #8
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Re: 700r4 rewire help!!!

come on someone has had to have ran into this.... I know I'm not the first to have taken off all this california smog crap.?.?. I even called my trans guy and he tried telling me that the 700r4 doesnt go to the computer
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Old 03-06-2013, 08:54 AM   #9
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Re: 700r4 rewire help!!!

Your mechanic is right. ECM does not control lock up. Go down to the trans driverside. If you have not removed the transmission, wiring should be connected to it. Follow the wiring up into the engine bay. Where does it end?

I ditched all lockup connections on my truck. I installed a 2500 stall converter. It locks in at 2500 RPM. It does not matter if I'm driving in OD or 3rd. Great performance. When it locks, you can feel the engine pull the truck up to throttle speed.
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Old 03-06-2013, 09:30 AM   #10
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Re: 700r4 rewire help!!!

Does the computer on the 87' and up TBI trucks control the transmission? I thought I read somewhere that it did when I was looking for information on the VSS sensor. Since the 85' didn't have VSS it may be totally different.
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Old 03-06-2013, 09:38 AM   #11
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Re: 700r4 rewire help!!!

The 85 does have a VSS for cruise control. TBI uses a TV cable for transmission control. 87 may or may not control lock up. I'm not really sure. I would guess not since 700R4 and 4L60 transmission all have TV control.
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Old 03-06-2013, 11:05 AM   #12
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Re: 700r4 rewire help!!!

The day I was pulling all the wiring out for the ESC,Smog crap I did follow the wiring and it went down to the trans. Even though I cut the wires I can lay it on the ground and take a picture for ya. I would assume that the 700r4 still works as anyone elses would though surly that vacuum sensor was what controlled it in the computer? but it looks nothing like the ones that I have seen.
Yes, I think I am about to go to turbo style 700r4 as my trans guy called it. O and I just wanna say I dont have a mechanic no offense I work on my own stuff, electrical stuff isnt my stong suit well along with my spelling and paragraphing but I can turn a wrench, hmm start to a country song
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Old 03-06-2013, 06:01 PM   #13
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Re: 700r4 rewire help!!!

Only way to know for sure is to find a wiring diagram for a Cali 85 truck.
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Old 03-06-2013, 06:50 PM   #14
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Re: 700r4 rewire help!!!

Does your trans have what looks like a oil pressure sending unit on the right side screwed into a pressure port?
I think that the esc dist. used a sending unit in the trans to tell the ecm when to advance and retad timing. I think it worked when it went into 3rd gear. It's be along time since i messed with those crappy dist.
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Old 03-07-2013, 12:14 AM   #15
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Re: 700r4 rewire help!!!

CA emissioned trucks in 85 and 86 did NOT have the vacuum control TCC lockup systems. The TCC was indeed locked up by the ECM taking inputs from the vehicle speed sensor and the TPS sensor (in the carb). 700's had 14 different wiring configurations inside the trans and 6 outside but the most common one on 85-86 CA emissioned vehicles was 3 wires at the trans.

Term A was 12v power that came from the fuse block, passed through the brake light switch and entered the trans. (point in running it through the brake light switch is to drop power when the driver depresses the brake so as to ensure the converter is in an unlocked state) It also passes through a 2 wire pressure switch on the valve body (inside the trans) which is a 4-3 pulse switch. This allows for a momentary unlock of the TCC when a 4-3 downshift occurs.

Term B comes from the ECM, enters the trans and is connected to a one terminal, normally closed 4th gear pressure switch that opens and essentially "ungrounds" the wire when in 4th gear thus telling the ECM the vehicle is in 4th gear. The ECM at this point reduces the amount of EGR by changing the pulse width on the EGR solenoid.

Term C is not used

Term D is the control ground signal given by the ECM. Once the proper parameters are met, the ECM grounds this wire and the TCC locks up.

Here is what you do. Remove the pan from the trans, leave the 12v positive / power side alone (including where it passes through the 4-3 pressure switch and connects to the TCC solenoid). On the ground side of the solenoid (side that connects to terminal D of the connector), clip the wire about 4 inches from the solenoid. Also clip the wire to the normally closed 4th gear pressure switch about 2 inches from the pressure switch. Using a butt connector, connect the wire from the neg side of the TCC solenoid and the wire that goes to the normally closed 4th gear pressure switch together. Remove the normally closed 4th gear pressure switch and replace it with a normally open 4th gear pressure switch - AC Delco D74411B. Connect the terminal and reinstall the pan. Fill with fluid. (5 qts on a pan drop only) (you can cut back the now unused wires inside the pan and remove them)

You should now only have the ONE wire (the purple one, which should have 12v with the key on) connecting to the trans externally. The rest you can remove.
This set up will give you lockup in 4th gear. You don't really need it in any other gear and 700's do have the potential to overheat when driven for extended periods of time in 4th gear without the converter locked.

I wired mine similar to this when I built it but did it all with a relay mounted externally with corresponding plugs so as to have it a plug and play set up and keep the proper signal going to the ECM for CA smog reasons. Yes, we still have to smog 1985's here..........ugh.

Attached is pic of the stock wiring....

Hope this helps.
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Last edited by beamn7; 03-07-2013 at 12:47 AM.
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Old 03-07-2013, 12:56 AM   #16
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Re: 700r4 rewire help!!!

Quote:
Originally Posted by beamn7 View Post
CA emissioned trucks in 85 and 86 did NOT have the vacuum control TCC lockup systems. The TCC was indeed locked up by the ECM taking inputs from the vehicle speed sensor and the TPS sensor (in the carb). 700's had 14 different wiring configurations inside the trans and 6 outside but the most common one on 85-86 CA emissioned vehicles was 3 wires at the trans.

Term A was 12v power that came from the fuse block, passed through the brake light switch and entered the trans. (point in running it through the brake light switch is to drop power when the driver depresses the brake so as to ensure the converter is in an unlocked state) It also passes through a 2 wire pressure switch on the valve body (inside the trans) which is a 4-3 pulse switch. This allows for a momentary unlock of the TCC when a 4-3 downshift occurs.

Term B comes from the ECM, enters the trans and is connected to a one terminal, normally closed 4th gear pressure switch that opens and essentially "ungrounds" the wire when in 4th gear thus telling the ECM the vehicle is in 4th gear. The ECM at this point reduces the amount of EGR by changing the pulse width on the EGR solenoid.

Term C is not used

Term D is the control ground signal given by the ECM. Once the proper parameters are met, the ECM grounds this wire and the TCC locks up.

Here is what you do. Remove the pan from the trans, leave the 12v positive / power side alone (including where it passes through the 4-3 pressure switch and connects to the TCC solenoid). On the ground side of the solenoid (side that connects to terminal D of the connector), clip the wire about 4 inches from the solenoid. Also clip the wire to the normally closed 4th gear pressure switch about 2 inches from the pressure switch. Using a butt connector, connect the wire from the neg side of the TCC solenoid and the wire that goes to the normally closed 4th gear pressure switch together. Remove the normally closed 4th gear pressure switch and replace it with a normally open 4th gear pressure switch - AC Delco D74411B. Connect the terminal and reinstall the pan. Fill with fluid. (5 qts on a pan drop only) (you can cut back the now unused wires inside the pan and remove them)

You should now only have the ONE wire (the purple one, which should have 12v with the key on) connecting to the trans externally. The rest you can remove.
This set up will give you lockup in 4th gear. You don't really need it in any other gear and 700's do have the potential to overheat when driven for extended periods of time in 4th gear without the converter locked.

I wired mine similar to this when I built it but did it all with a relay mounted externally with corresponding plugs so as to have it a plug and play set up and keep the proper signal going to the ECM for CA smog reasons. Yes, we still have to smog 1985's here..........ugh.

Attached is pic of the stock wiring....

Hope this helps.
THANK YOU!!! Youre my hero I got it to fire up tonight, so hopfully this weekend Ill be able to get to the trans..
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