4L80e cooler line - which is the return?

[rockR67]

Hi All,

Going to do a filter and flush on the c2500. I usually pull a cooler line at the radiator end to get a full flush done - ideally the return line so the incoming line can pump old fluid out and through the coolers into a pan.

anyone know which of the two lines at the front is the retuen I want to disconnect? It could save me from a big messy guess and check. Thanks!

 

[Supercharged111]

If it's the 99, return should be the rear line.

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[rockR67]

Right, 99 - thanks that’s very helpful.