Gen 5, LT4 wiring
07-21-2023, 09:14 PM
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Gen 5, LT4 wiring I am doing a Gen 5 LT4 swap into an 86 2wheel drive Blazer. 4L75E transmission. The transmission control module harness has a 4 wire leg with a square plug on the end. It is labeled as follows: A: gray, brake light. B:blue, Cal.A/B. C:green, cancel od. D:yellow, dyno. I assume that this is supposed to plug into some kind of brake switch or brake pedal position sensor. However, I have not been able to find either that will match this plug. The local dealer where I bought the package is no help and the Chevy performance tech line will not talk to me since I am not a dealer. Can anyone help? I have done several LS swaps but the LT4 is a completely different animal.
07-30-2023, 07:48 PM
#2
I am doing a Gen 5 LT4 swap into an 86 2wheel drive Blazer. 4L75E transmission. The transmission control module harness has a 4 wire leg with a square plug on the end. It is labeled as follows: A: gray, brake light. B:blue, Cal.A/B. C:green, cancel od. D:yellow, dyno. I assume that this is supposed to plug into some kind of brake switch or brake pedal position sensor. However, I have not been able to find either that will match this plug. The local dealer where I bought the package is no help and the Chevy performance tech line will not talk to me since I am not a dealer. Can anyone help? I have done several LS swaps but the LT4 is a completely different animal.
07-31-2023, 05:22 PM
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I was finally able to contact a tech at Chevy performance. He told me to cut the plug off . The gray wire is the only wire used. It is to be connected to the brake switch and sends a 12 volt signal to the TCM when the brake is applied., unlocking the converter. There are a lot of unused wires in the harness. Thanks for your reply.
08-01-2023, 05:48 AM
#4
Why not go with a better transmission if you’re going through all the trouble of swapping in a gen v LT engine? The 4l60-75’s are terrible and one of the worst transmissions that gm ever made... Gas mileage alone will be worth it and drivability etc will improve as well. Id consider at least a 6l90e but to each his own.