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**pjmoreland** · 11-03-2022, 04:20 PM

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.

11-03-2022, 04:20 PM	#140
pjmoreland Senior Member Join Date: Jan 2005 Location: CA Posts: 5,355	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.