Hi, if you were on a steep enough incline, what you said makes sense..
The easy was to check cooler flow with out any a flow meter, on the C6,the cooler return line is the rear line.
After refilling the trans and running it a few minutes to circulate the fluid, not long enough to get it hot , a few minutes is enough
Disconnect the rear line & slip a piece of hose over the line & run it down toward the floor...If you set a quart jar into a hog pan (in case of overflow)..have an assistant start the truck while you watch the jar fill up, you can use a can, but a jar will provide a better view.
At engine idle your cooler should flow about a quart in 20 seconds at idle...........Donnie
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