PSA check your wiring.

[skylark]

These connectors came from a 99 Suburban with a 4L80e. It shifted without any kind of issue whatsoever but when the harness was stripped back this was the damage that I found. I would have never found this damage if it wasn't for the fact that we were using this harness in an LS swap. The input shaft speed sensor connector is also bad but it wouldn't show up good enough in a picture.

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[mars2878]

Damn

 

[Daddyoh]

Wow, that is terrible. It looks like it was done by heat. The insulation I believe is Teflon it should not have melted like that.

 

[skylark]

Wow, that is terrible. It looks like it was done by heat. The insulation I believe is Teflon it should not have melted like that.

What is odd is that I won't usually see brittle insulation with wires getting crispy. In this case the insulation is completely flexible.

 

[Supercharged111]

My neighbor found that same thing on a truck he was working on at his shop. I want to say it too was a 4L80.