Its about 3200 or so. The reason the redline is so high is because when your in tow haul and coming down a hill with a trailer the trans will downshift and use the engine as a brake to slow the truck and the RPMs can go up into that range.
The older trucks have a dashed redline starting around 3200 but people would come into the dealer thinking there is a problem when the Tach shows 4500 coming down a hill. If you touch the gas it upshifts so you can't operate it in that range but it works great as a speed brake.
So GM took out the dashed Redline so the idiots would quit complaining that something is wrong.
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