#1057864 - 06/20/18 01:37 AM
Re: 700R4 tq conv unlock?
[Re: siberhusky0]
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Joined: Dec 1999
Posts: 11,373
86ttop
15+ Year
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15+ Year
Member

Joined: Dec 1999
Posts: 11,373
Brooksville, Fl
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ChasUno, he's talking about an aftermarket vacuum switch that opens the circuit when vacuum goes low ,like on acceleration, it opens the electrical circuit and the trans unlocks when there is no voltage.
Leo Paugh It's not an attitude, it's just the way I am. POW*MIA You are not forgotten If things improve with age, I must be approaching magnificent.
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#1057869 - 06/20/18 05:58 AM
Re: 700R4 tq conv unlock?
[Re: siberhusky0]
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Joined: Jun 2016
Posts: 328
ChasUno
Member
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Member

Joined: Jun 2016
Posts: 328
Bradenton, FL
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I dug out my GM service manuals (1988 Caprice and Monte Carlo) and did some reading. These manuals also include details on the 700 R4 trans as well as the 200 4R. Looking at the electrical manual, there doesn't appear to be anything electrical for TCC operation other than 3rd and 4th gear switches (outside of any ECM operation). I couldn't find anything that indicates that the TV cable triggers any switches in the trans. ![[Linked Image]](https://i.imgur.com/kpAa3ZF.jpg) Looking in the big GM service manual, that seems to be confirmed when looking at the 700 R4 TCC transmission section (n.b., there appears to be numerous variations of electrical wiring types for this system, but they all seem to center on 3rd and 4th gear switches inside the transmission itself). ![[Linked Image]](https://i.imgur.com/eEGICuL.jpg) ![[Linked Image]](https://i.imgur.com/lwxfuh1.jpg) As you aren't running the ECM and have a manual TCC switch, it seems that only 3rd and 4th gear switches can affect TCC operation. My understanding of looking at the wiring diagram is that the 4th gear switch needs to be closed for TCC to operate. I can't tell if it will lock in both 3rd and 4th, but there's a lot of mentioning of a 4th to 3rd downshift, which I think operates a switch that causes the electrical supply to the TCC solenoid to be cut, thus disengaging the TCC. Once the transmission moves back up into 4th, then the circuit is once more completed and the TCC is engaged.
1986 Monte Carlo SS
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#1057888 - 06/21/18 02:09 AM
Re: 700R4 tq conv unlock?
[Re: siberhusky0]
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Joined: Dec 1999
Posts: 11,373
86ttop
15+ Year
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15+ Year
Member

Joined: Dec 1999
Posts: 11,373
Brooksville, Fl
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It can be done with a toggle switch, but requires driver turning the switch on and off.
Leo Paugh It's not an attitude, it's just the way I am. POW*MIA You are not forgotten If things improve with age, I must be approaching magnificent.
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#1057892 - 06/21/18 05:20 AM
Re: 700R4 tq conv unlock?
[Re: siberhusky0]
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Joined: Jun 2016
Posts: 328
ChasUno
Member
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Member

Joined: Jun 2016
Posts: 328
Bradenton, FL
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Found some more details about the700 R4 TCC and lock up operation in my GM Service Manual. Some of the information is scattered around a bit, so it took a good bit of reading to locate some of the specifics. Introduction to the TCC: ![[Linked Image]](http://i.imgur.com/L1TvxBw.jpg) ![[Linked Image]](http://i.imgur.com/ieilBJm.jpg) Diagnostics: ![[Linked Image]](http://i.imgur.com/OIC9RjI.jpg) ![[Linked Image]](http://i.imgur.com/WXWirmO.jpg) What I understand, is that these circuit diagrams show that for a standard ECM equipped car to engage TCC lock up, the following conditions must be met: 1. VSS (speed) - must be greater that a specified amount 2. Engine Coolant - must be at normal operating temperature 3. TPS (throttle position sensor) must be showing a steady reading 4. 4th gear switch in transmission must be engaged 5. Brake pedal must be off If these five conditions are met, then the ECM sends the signal to activate the TCC lock up solenoid and allow lock up to occur. If anyone of these conditions deviates from its specific parameters, then TCC lock up will disengage. However, in the case of a car with the ECM removed, then the first four parameters do not come into play. The manual switch you have effectively bypasses these four requirement and activates the lock up solenoid regardless of these conditions. The last parameter does still apply though, so if you have the the TCC engaged and then you press the brake pedal, that interrupts the solenoid by breaking the circuit. As soon as the brake pedal is released, then the circuit is completed and the solenoid will re-lock the TCC. Unlike the 200 4R, the 700 R4 uses the 4th gear switch in the transmission to tell the ECM it is in 4th gear, and then then ECM reads the other 3 parameters to decide if conditions are met for it to engage the solenoid. However, there is no ECM input in your car so this does not apply. Therefore the only way the transmission will come out of a manually activated lock up is if it changes down a gear from 4th. Then the internal 4th gear selected (or 4 - 3 downshift) switch in the transmission will trip, and interrupt the power supply to the lock up solenoid. The only bit in the manual that I don't quite understand is this: "A 4th gear switch (mounted in the transmission) opens when the trans shifts into 4th gear and this switch is used by the ECM to modify TCC lock up and unlock points, when in a 4 - 3 downshift maneuver." I get that the ECM wants the trans to be in 4th before it allows lock-up, but I'm not sure what it means by adding "when in a 4 - 3 downshift maneuver"? If it downshifts from 4 -3, then the 4th gear switch will be deactivated? Or maybe it does something specific during the 4 - 3 downshift? Again though, with no ECM in place, this wouldn't occur with a manually activated TCC lock up.The only way a manual TCC lock up can be disengaged is if the brake pedal is pressed, the transmission drops out of 4th gear or the driver deactivates the manual TCC switch.
1986 Monte Carlo SS
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#1058210 - 07/11/18 01:24 AM
Re: 700R4 tq conv unlock?
[Re: siberhusky0]
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Joined: Feb 2016
Posts: 34
siberhusky0
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Member
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Posts: 34
Kelso, WA
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Alot of good info, thanks. I still have no idea what tells the TCC to unlock under a load with no computer or vacuum switch installed. It will lock up in 2nd, 3rd & 4th when the the switch is activated & supply's 12V to TCC soleniod. In 3rd or 4th with TC locked, give it a bit of throttle & it unlocks, maintain the same throttle setting & when the speed catches up & not adding torque, it locks again. Don't know about in 2nd, no reason to use it. If in 3rd with the TC locked & with a manual shift to 4th, it does not unlock. An auto 3-4 shift & TC locked is the same, no unlock. A forced 4 -3 shift it will unlock. A manual 4 - 3 shift it will stay locked if off the gas or if power is maintained. I don't know how or where it takes place, but the unlock has to be controlled by pressure since there is nothing other than a on/off switch & brake to interrupt power to unlock. There is a single wire under the pan from where power comes in to what I assume is the 4th gear switch & from there to the TCC solenoid. It's a mystery to me & didn't give it a thought until I did the manual lock up & was curious as to why I didn't a vacuum switch.
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