Re: 700R4 TCC Wiring
 

You are 100% right. I'm hoping to get away with being able to use the stock cable that comes with the speed sensor to simplify the wiring. I will switch to shielded/twisted pair cabling if the latest setup doesn't end up working reliably. Some of the electrical noise issues may be inside the controller box itself.

Re: 700R4 TCC Wiring
 

I've done a couple of hour+ freeway drives over the last few days, and the TCC controller is working consistently with no glitches.

I'm considering moving the vacuum sensor to manifold vacuum instead of the timed vacuum port on the carb because it is slightly distracting to have the TCC unlock and then re-lock every time I coast momentarily due to traffic. I'm not sure there would be a downside to this change. I was using timed vacuum for my old vacuum switch & delay relay setup to unlock when coasting down to a stop. That's no longer necessary because the Arduino will unlock under 45mph.

Re: 700R4 TCC Wiring
 

I moved the vacuum sensor from timed vacuum to manifold vacuum. This change keeps the TCC locked when coasting. I like this better because I found it distracting to have the TCC unlock and relock each time I let off the throttle in traffic. Initially I connected the sensor to the same vacuum fitting that my brake booster is connected to on the rear of the intake manifold, but for some reason the vacuum level was erratic there. I ended up teeing into the hose that runs from the front of the carb to the distributor vacuum advance.

Re: 700R4 TCC Wiring
 

Hello sir, I am helping my brother with his 1987 GMC Jimmy and came across your arduino torque converter control project. His Jimmy was originally a TBI engine with a 700R4, we have now converted it to carburetor. So we need a way to control the lockup of the converter. After looking at the vacuum switch options, I felt like there must be a better way. Since I have worked with arduinos previously, I searched and came up with your posts.

I would love to get a copy of your gerber files and the arduino sketch. I looked over your parts list and I am thinking I might be able to use an OEM 1bar MAP sensor in place of the NXP sensor you used. It is a 0-5V sensor, and I already have one handy. Any thoughts on that sensor?

Re: 700R4 TCC Wiring
 

Sounds like a fun project you've got there. I'd be happy to share the files with you. I received your private message, so I will send you an email shortly. I had to order five PCBs, so I've got four extras. I can drop one in the mail to you, if you'd like. If the MAP sensor is 0-5V, then it should work.

Re: 700R4 TCC Wiring
 

Posted in error.

Re: 700R4 TCC Wiring
 

Send me a private message with your mailing address, and I'll send you a board for free.

Re: 700R4 TCC Wiring
 

Got your email with the files, and sent you my address.

I appreciate the help. I will follow up in this thread or another with the results using the OEM GM sensor.

I deleted the post from my other user name 67Fbird to avoid confusion (duplicate account created due to registration issues).

Re: 700R4 TCC Wiring
 

I'll mail the PCB out tomorrow.

Re: 700R4 TCC Wiring
 

Got the PCB today, thanks again for sending it.

It is crazy cool that places like JLPCB exist, and awesome that they can make custom PCBs for such a reasonable price. Just a few years ago our options would have been a protoboard or DIY etching.

I made a little progress on testing the GM sensor (PN: 16187556). I used an analog vacuum source to test from 2 inHg to ~25 inHg. The output was rock solid stable and very linear as shown in the graph.

I was not able to find a data sheet on this sensor, so I also tested the current draw over the range of vacuum. It was 0.006A.

So it looks like this sensor will work for my brother's truck. I am going to go through my parts I have on hand and make a Mouser order to complete it.

Re: 700R4 TCC Wiring
 

That looks really good. The spec sheet for the vacuum sensor I used says the typical current draw is 6mA too.

https://www.nxp.com/docs/en/data-sheet/MPXV6115V.pdf

Re: 700R4 TCC Wiring
 

I did some rerouting of the vacuum line that goes to the TCC controller box. I added an OE vacuum gauge to my gauge cluster, so I used a little metal 1/8" barb tee fitting to tie into the line going to the gauge. This allowed me to eliminate the rubber hose that was teed into the distributor vacuum advance hose. I also replaced the firewall grommet with an OE one that had two holes. I added a third hole for the vacuum line.

Re: 700R4 TCC Wiring
 

I purchased a 1989 K1500 recently that has a 700R4. It has been interesting to observe the behavior of the TCC lockup logic. Under light acceleration, it seems to lock the TCC at quite a low speed, like around 35MPH. It does unlock it quite readily with increased acceleration though. Personally, I prefer having the TCC lock at speeds over 45MPH, as it lugs the engine less that way. Also, I could be wrong, but it seems to lock the TCC even if I have shifted manually to "D" (third gear). Also, the TCC seems to unlock when coasting.

Re: 700R4 TCC Wiring
 

I'm not an expert but I'm fairly certain in that year the lockup was controlled by pressure to the 3 or 4 gear circuit. Pump pressure varies with speed. That's why it unlocks when coasting as the pump isn't being driven fast enough.
There may be a pressure issue or component failing to causing the 35mph lockup. My 91 S10 locks up in 45 to 50 mph range. You might drop in to this thread and ask it it is a problem.

http://67-72chevytrucks.com/vboard/s...d.php?t=634121

And I got your prototype installed but I wasn’t able to get it to work so I pulled it out to bench test it and then my laptop went sideways. So the laptop is at my buddies for resurrection. More to follow.

Re: 700R4 TCC Wiring
 

I was expecting it to lock at 45MPH+ like your 91 S10. According to the document posted in the following thread, my 89 K1500 with a 5.7 is a 9TXM model which is wired in the #18 style. The TCC is controlled by the ECM in this style, which I take to mean that the ECM decides when to lock the TCC based on things like vehicle speed, throttle position and manifold vacuum level.
https://67-72chevytrucks.com/vboard/...15#post8974715

That's a bummer that the controller didn't work. It might require driving around with a laptop connected to it with some print statements added to to code to see what's working and what's not. I would start by printing the speed and vacuum level. It could be that I made some mistakes with the code I added to ignore the 4th gear switch signal for your TH350C.

Re: 700R4 TCC Wiring
 

Does the speedometer seem accurate? Those early electronic speedometer systems are funky and if someone mixed and matched parts in the past you could have a speed error.



That's the plan when the laptop is back. First test the brake and vacuum inputs while faking the speed input to see if it provides a solenoid output on the bench.
Then plug it back in the truck and throw some jack stands under the rear axle to check the speed input and solenoid output.

Re: 700R4 TCC Wiring
 

The speedometer does seem accurate. I haven't tested it with a GPS, but it is smooth and consistent, and my gut says it's about right. I will do a GPS test.

I wonder if there's something going on with the temperature switch inside the transmission. I believe it can cause the TCC to lock up sooner than normal. It could also be that someone swapped in a transmission from another year that doesn't have the correct internal wiring. I'll need to drop the pan soon to do a filter service on it anyway, so I'll take a look.

Re: 700R4 TCC Wiring
 

I found a bug in my Arduino code for the TCC controller that was making the calculated speed value 1/5 of what it should have been. I wanted to lower the TCC off vacuum level in my unit today, so I made the tweak to the latest version I had archived and uploaded it. Then the controller wouldn't work. I turned on some print statements, drove down my driveway with the serial monitor open on my laptop, and noticed that the speed value was way off. I took a closer look at the code, and noticed that the last bit of code I had modified a year ago was incomplete. I had increased the number of speed readings that get averaged from 8 to 40, but one line still had 8 in it. Once I changed the 8 to a 40, it started working again.