73-87 Chevy _ GMC Trucks > Electrical

TCC lockup pin location

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frotosride:
Looking for where the torque converter lockup (+) purple wire pins in at the firewall. Honestly can't remember if it is a separate plug/connection or if it was originally on the main bulkhead for the fuse panel. It's been so long that I can't remember where I de-pinned it from.

1987 V10 Silverado 700r4

bd:
The purple wire (Ckt 420) supplies I+ to the TCC solenoid from the brake switch.  It routes through the firewall bulkhead connector as shown.  Is this the wire you are questioning?

frotosride:
Thank you, I swear I looked through all of the diagrams listed for '87 but couldn't find this diagram. The ones listed/pinned say 1987 but are printed for 1988 and have more pins. I almost just put it back together where ever I had a free spot. But I stopped so I can do body mounts. I did find #420 on the other chassis diagrams but the bulkhead connectors didn't look right.

Did you pull this sketch from the ones pined above?

frotosride:
I have kept the brake switch without vacuum hooked up. I'm letting the Terminator handle (-) control for the relay and the brake switch (+) for tcc lockup. Also plan to use the 4th gear grounding circuit as input for possible future tuning configs.  Thanks again

bd:

--- Quote from: frotosride on June 12, 2026, 07:48:37 pm ---Did you pull this sketch from the ones pined above?

--- End quote ---

I compiled the diagram from two separate diagrams illustrated in the '87 factory wiring manual.  It took a minute because there are circuit omissions in the diagrams that obstruct easy correlation.  You're welcome!

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