700R4 TCC Wiring

[Accelo]

Originally Posted by tdangle

Yes exactly the same for 2004r and 7004r.
the most simple setup is to run a wire from the + side of the TCC solenoid to power thru a switch. Once your in 4th, flip the switch feeding +12v to the TCC solenoid and it will lock, when the trans downshifts to 3rd or lower, the pressure switch opens and you no longer have ground to the solenoid thereby unlocking the converter.

With this setup it will greatly extend your stopping distance at highway speeds. Because you will have to drag down the motor and the vehicle with the brakes till the vehicle wheels go below shift speed to 4th. I would do the same thing but include a brake switch with the connections for the brake lights and the unlock for the converter. Run the wiring through the switch first. However it will work both ways. I just prefer the fastest stopping distance possible.
Rick

[tdangle]

Originally Posted by Accelo

With this setup it will greatly extend your stopping distance at highway speeds. Because you will have to drag down the motor and the vehicle with the brakes till the vehicle wheels go below shift speed to 4th. I would do the same thing but include a brake switch with the connections for the brake lights and the unlock for the converter. Run the wiring through the switch first. However it will work both ways. I just prefer the fastest stopping distance possible.
Rick

I didn't say this was the best setup, but the most basic simple setup. I started with mine locking up when going into 4th power running thru a dual brake light switch. then added the electronic delay and vacuum setup. I would really like going to a 4l65e with a standalone controller but when I add everything up I'm getting over 4K probably closer to $4500 and that is a hard one to justify. If my 2004r dies, I'll probably switch to a 7004r as it is more supported and I'll be able to tune the governor part throttle shift points a lot easier than the 2004r

[pjmoreland]

Having the TCC lock momentarily every eight seconds when driving at a medium speed up a hill is getting on my nerves. Adjusting the relay time delay and the vacuum switch trip point just causes the issue to occur in a slightly different driving scenario, but the issue is still there. I think what I need is some hysteresis in the vacuum switch (two different vacuum levels for on vs. off). I could achieve this by rewiring my current vacuum switch so that the relay gets latched on so once the vacuum switch turns on the relay, the relay stays on even if the vacuum switch turns back off. I'd then need a second vacuum switch to break the relay latch connection once the vacuum dropped off significantly. I'm going to order a second vacuum switch so I can give this a try. Does this make sense?

*low vac = numerically low vac = pressing down on the accelerator

Edit: This schematic is missing a necessary diode shown in a later post.

[tdangle]

Originally Posted by pjmoreland

Having the TCC lock momentarily every eight seconds when driving at a medium speed up a hill is getting on my nerves. Adjusting the relay time delay and the vacuum switch trip point just causes the issue to occur in a slightly different driving scenario, but the issue is still there. I think what I need is some hysteresis in the vacuum switch (two different vacuum levels for on vs. off). I could achieve this by rewiring my current vacuum switch so that the relay gets latched on so once the vacuum switch turns on the relay, the relay stays on even if the vacuum switch turns back off. I'd then need a second vacuum switch to break the relay latch connection once the vacuum dropped off significantly. I'm going to order a second vacuum switch so I can give this a try. Does this make sense?

*low vac = numerically low vac = pressing down on the accelerator

Can you adjust your vac switch to a lower setting, say only below 5 inches the TQ unlocks? This might help prevent the cycling going up a hill. Monitor your vacuum with a gauge while driving to see what the actual conditions are might shed some light on it.

[pjmoreland]

Originally Posted by tdangle

Can you adjust your vac switch to a lower setting, say only below 5 inches the TQ unlocks? This might help prevent the cycling going up a hill. Monitor your vacuum with a gauge while driving to see what the actual conditions are might shed some light on it.

I did try that, and it quit cycling on mild hills. Instead, the cycling then started happening on more aggressive hills at higher speeds. I think there will always be a scenario where it cycles if there is no hysteresis in the switch. I will be testing the dual switch setup in the next day or two. This will give me adjustable hysteresis.

[pjmoreland]

I added a second vacuum switch this evening, and it solved the cycling problem. I had to add a diode to the relay latching connection to prevent voltage from backfeeding through the low vacuum switch to the TCC. Without the diode, the delay relay was being bypassed.

I have the low vacuum switch set at 3inHg and the high at 6inHg. I'm going to experiment with setting the low switch even lower so that the TCC stays locked up under heavier load than it does currently. My engine can handle a little more lugging than is allowed at the moment, especially at highway speed.

I've included an overall photo of the harness, but it was from before I installed the diode in the short red wire.

[pjmoreland]

I ended up adjusting the low vacuum switch to 2inHg and the high to 9inHg. With this setup, it waits longer to lock the TCC in scenarios like accelerating onto the highway due to the higher high switch, but then once it finally locks the TCC, it stays locked longer under heavier load like from a gradual hill on the highway due to the lower low switch. Basically, it doesn't want to lock as easily, but once it does lock, it is more likely to stay locked. This is also good because it prevents the on/off cycling I was having when I had just one vacuum switch.

[pjmoreland]

700R4 transmissions from 1989-93, I believe, had a temperature switch that would close if the transmission overheated, causing the torque converter clutch to be locked in 4th gear regardless of the state of the vacuum or speed sensors and the logic of the ECM. The way I have wired my TCC has rendered the temperature switch ineffective. Here's another way the TCC could be wired that would have all of the same behavior of my current harness, but it would also allow the temperature sensor to work as GM intended.

[custom10nut]

Sub’d for future reference

[pjmoreland]

I redid my TCC harness today according to the schematic in post #33 above. It works just the same as my previous harness, except now the internal transmission over-temperature switch should be active. I have no good way to test the temp switch, but I suppose I might find out if it works someday if my transmission overheats and the TCC locks in 4th regardless of what the vacuum switches and relay are trying to do.

One minor issue I've noticed is that if I'm cruising along in 4th with the TCC locked and I coast down to a very low speed, the transmission stays in 4th and the locked TCC really lugs my engine and causes it to stutter a bit. I noticed this in stop-and-go traffic the other day. Connecting both of the vacuum switches to the carb timed vacuum port would solve this issue by unlocking the TCC whenever I'm coasting. I don't like this solution as I mentioned in a previous post because it makes for an unnatural driving experience when coasting and reapplying the accelerator at higher speeds. A partial solution to this issue is to connect only the high vacuum switch to timed vacuum. This will prevent the TCC from re-locking after tapping the brakes to coast down to a low speed. At the same time though, this will not unlock the TCC at higher speeds when coasting periodically because the high vacuum switch is ignored by the circuit once the TCC is locked.

The ideal solution for the low-speed lugging issue would be to install a B&M 70244 speed-based TCC controller, and use its output signal to power my harness instead of tapping into the 12V from the Tail Stop fuse. This way the TCC could be prevented from locking altogether under, say, 35mph, but the vacuum switches and delay relay could still function as I have them functioning at higher speeds. I doubt I'll go this route though because the B&M controller is $242.

*EDIT* - The internal switch in the transmission is the 4th gear switch, not the 3-4 switch as it says on the schematic below

[Chris_oz]

Wow, I love the quality of your work, looks factory and very neat.

I have a 1993 TH700 in my 62 Cadillac and wanted to have some control over the TC locking with buying a kit, as I am in Australia, everything is 3 times the price by the time its landed here.

I used the brake switch, so it controls all, brakes on, its unlocked.
I also put in a 3 position, 2 way switch, so I can have OFF, on in 4th only, or on in 2nd-3rd-4th (still has brake switch)

I use the factory 4th gear switch to earth when in the 4th switch position, and use the switch to earth for 2-3rd gear.
I seldom use this function other than when driving down long flowing hills, 3rd gear, TC locked is perfect for light throttle and strong engine brake, I manually select 3rd on the shifter and flip the switch.

My trans was out of a lighter sedan, so had a light Gov in it, making the 1-2 and 2-3 upshifts way to late for my driving style, I added some weight with the stock springs and got it so I now have a nice relaxed shift on light throttle.

my 3-4 upshift is at 50-52 mph, which is perfect for me, as many of our local roads are 50mph limit, so I can get it to drop into 4th very easily, but a slight press on the gas has it back to 3rd, so it works for me.

I have wondered about a vacuum switch, as very rarely I feel it labor on slight hills, not enough to make it change back, but enough to load it and have wondered if a vacuum switch could be tuned to help here, but I normally just flick the switch.
I have been thinking about putting in a second headlight dipper switch (floor mounted) to turn it off. might be a good winter project.

[pjmoreland]

My 700R4 was out of a 93 Caprice with a 305. I need to play with my governor to see if I can increase the RPM of the part-throttle 3-4 shift a bit. It would be nice if the 4-3 shift happened at a higher RPM too when coasting to a stop. It hangs on way too long right now.

[HotWheelsFan]

I love the write up. I also like your thinking in the creation of you homemade middle of the road controller.

Had similar ideas in the past myself but never used the 700r4 long enough to fine tune things.

I would like to mention that you have test port plugs on the transmission that lead to certain fluid circuits in the trans. Without getting my books out to see which ones you may have on your model year... You may want to look and see when each one's get pressure during certain conditions.

You may find one that can work an oil pressure switch that may be activated when vehicle speed drops.

Another thought is downshift from 4th to 3rd calibration...

Of course, you could add a speed sensor and use a little electronic engineering to operate a switch or control under certain conditions - Outside my abilities to design, but understand electronic engine controls theory.


Once again, love the work your doing.

Bob

[pjmoreland]

Originally Posted by HotWheelsFan

I love the write up. I also like your thinking in the creation of you homemade middle of the road controller.

Had similar ideas in the past myself but never used the 700r4 long enough to fine tune things.

I would like to mention that you have test port plugs on the transmission that lead to certain fluid circuits in the trans. Without getting my books out to see which ones you may have on your model year... You may want to look and see when each one's get pressure during certain conditions.

You may find one that can work an oil pressure switch that may be activated when vehicle speed drops.

Another thought is downshift from 4th to 3rd calibration...

Of course, you could add a speed sensor and use a little electronic engineering to operate a switch or control under certain conditions - Outside my abilities to design, but understand electronic engine controls theory.


Once again, love the work your doing.

Bob

That's a very interesting idea about the pressure test ports. I'm totally ignorant about those, so that will give me something to look into. Thanks!

[HotWheelsFan]

Yea, have no idea if they could help. Just keep in mind how much pressure could be seen at any certain test port point. Not sure what a pressure limit may be on a oil pressure switch ether.

I have seen them on trannys in the past, might have been on imports, can't remember.

[Chris_oz]

Originally Posted by HotWheelsFan

I love the write up. I also like your thinking in the creation of you homemade middle of the road controller.

Had similar ideas in the past myself but never used the 700r4 long enough to fine tune things.

I would like to mention that you have test port plugs on the transmission that lead to certain fluid circuits in the trans. Without getting my books out to see which ones you may have on your model year... You may want to look and see when each one's get pressure during certain conditions.

You may find one that can work an oil pressure switch that may be activated when vehicle speed drops.

Another thought is downshift from 4th to 3rd calibration...

Of course, you could add a speed sensor and use a little electronic engineering to operate a switch or control under certain conditions - Outside my abilities to design, but understand electronic engine controls theory.


Once again, love the work your doing.

Bob

Mine is a late one, it has no external test ports, I saw a video showing where to drill. I would like to have a 3rd switch.

[tdangle]

I've had the same issue with slowing down and lugging. Thats why I installed the vac switch. It eliminates that issue. The only issue I have is if I try to drive in D not 3rd around town, it shifts into 4th way too early. then the converter locks, vac drops it unlocks then locks back up 8 sec later. I've not found a way to avoid this and as a result drive in 3rd around town. Kinda sucks. I thought about the B&M speed based unit but like you have a problem with the cost. No way it should cost that. I would actually love to have a 4L60 but when your done, it looks like $4500 or better. Be nice to have the response of a modern car as to when it shifts and locks. Oh Well, guess I have to live with it.

[pjmoreland]

Originally Posted by tdangle

I've had the same issue with slowing down and lugging. Thats why I installed the vac switch. It eliminates that issue. The only issue I have is if I try to drive in D not 3rd around town, it shifts into 4th way too early. then the converter locks, vac drops it unlocks then locks back up 8 sec later. I've not found a way to avoid this and as a result drive in 3rd around town. Kinda sucks. I thought about the B&M speed based unit but like you have a problem with the cost. No way it should cost that. I would actually love to have a 4L60 but when your done, it looks like $4500 or better. Be nice to have the response of a modern car as to when it shifts and locks. Oh Well, guess I have to live with it.

Installing a second vacuum switch like I did resolved the on, off, 8 seconds, on, off, 8 seconds issue on hills. I just got back from a test drive after connecting my high vacuum switch to timed vacuum from the carb, and now the TCC stays unlocked when coasting after tapping the brakes. This cuts down on lugging at slow speeds.

I'm thinking about installing a Sonnax AS1-01K TV cable corrector kit, which would allow me to run the TV cable a little tighter than normal so the part throttle shift points would be moved up without increasing WOT shift points. That should also help with lugging.

[pjmoreland]

I found a functional TCC vacuum switch in a 1984 Chevy van today and did a little test on it to see how it behaves. It has some hysteresis built into it (about 2 inHg) unlike the vacuum switch TCI sells. Here's a little video I made to demonstrate its behavior:

https://youtu.be/McejhiEMph8

[pjmoreland]

I realized I had the vacuum delay valve hooked up backwards in the previous video I posted, so I redid the video. The delay valve is supposed to delay turning on the vacuum switch. The blue side of the vacuum delay valve faces toward the vacuum switch. Here's the new video.

https://youtu.be/McejhiEMph8

GM 15599002 Vacuum Switch
EC301 Borg Warner Vacuum Delay (substituted in for GM 14020691)

The orientation of the vacuum delay valve can be seen in this thread:

http://67-72chevytrucks.com/vboard/s....php?p=1230774

[pjmoreland]

In case anyone is interested in seeing how the 14020691 vacuum delay valve works in the video I posted above, I cut mine open. The little orange rubber circle is a check valve that allows pressure to flow freely toward the vacuum switch to turn it off quickly when the accelerator pedal is pushed down. The smaller silver circle is a restricted passageway that allows vacuum to build slowly on the vacuum switch.

The reason this vacuum delay valve was not working was because there was a little bit of gunk under the orange check valve. A few sprays of carb cleaner probably would have fixed it. Oh, well.

[pjmoreland]

I've been trying to avoid this, but I've decided to go down the road of using an Arduino microcontroller to control the TCC. The main reason is to prevent lockup at low speeds. I'm going to use a speed sender from Dakota Digital (they make cruise control kits). I'm also going to use a vacuum sensor instead of vacuum switches so I can make easy adjustments to the trip points. The speed sender is backordered 4-6 weeks, but I played around with the vacuum sensor and an Arduino Nano Every today. It worked quite well.

[pjmoreland]

I received the speed sensor I ordered from Dakota Digital and hooked it up to the Arduino. The signal from the speed sensor is sinking (ground), so it took me a little while to figure out I needed to activate the INPUT_PULLUP setting on the digital input that is reading the speed sensor signal. Spinning the speed sensor at about four revolutions per second should be the same as 15 mph, and that's what I'm reading. The next step is to wire this up to my truck in a temporary way so I can start reading the 4th gear switch and activate the TCC solenoid.

[HO455]

Definitely interested in this! I have been playing with an Arduino and a spare speed signal generator from my Gearvendor. Big learning curve for me.
I have a TH350C transmission in front of the Gearvendor and my earlier attempts to use vaccum switches didn't work out very well. I couldn't stop the detonation caused by having the converter locked up at lower speeds during part throttle acceleration. I feel that keeping the converter unlocked below 45 mph in conjunction with a vaccum switch should solve my pinging issue.
I have experienced poor life span with the TCI style vaccum switches. The diaphragms fail giving me a vaccum leak. So I am interested in the vacuum sensor you have sourced too. Using a sensor should give you the ability to set the hysteresis to what ever you want. Good idea.
I have also thought about installing a ECU from an early TH350C car in the truck as a low cost MPH switch. I just haven't found one in the wrecking yard yet.

[pjmoreland]

Originally Posted by HO455

Definitely interested in this! I have been playing with an Arduino and a spare speed signal generator from my Gearvendor. Big learning curve for me.
I have a TH350C transmission in front of the Gearvendor and my earlier attempts to use vaccum switches didn't work out very well. I couldn't stop the detonation caused by having the converter locked up at lower speeds during part throttle acceleration. I feel that keeping the converter unlocked below 45 mph in conjunction with a vaccum switch should solve my pinging issue.
I have experienced poor life span with the TCI style vaccum switches. The diaphragms fail giving me a vaccum leak. So I am interested in the vacuum sensor you have sourced too. Using a sensor should give you the ability to set the hysteresis to what ever you want. Good idea.
I have also thought about installing a ECU from an early TH350C car in the truck as a low cost MPH switch. I just haven't found one in the wrecking yard yet.

I agree 45 mph would be a good cutoff. I am not sure if I'm going to be able to make the vacuum sensor work to my satisfaction. My impression is that you don't have to press the gas pedal down very far to make the vacuum level go almost completely away. I'd like to have the TCC stay locked maybe all the way to half throttle. Maybe a pedal-mounted switch from a 71-72 truck with a TH400 would be a better way to go. Another approach might be to tap into one of the pressure ports on the side of the 700R4 transmission to read the pressure associated with the TV cable position. I have thought it might work well to base the decision to lock or unlock the TCC on whether the gas pedal has been pressed down slowly vs. quickly.