2007 Sierra Denali Transmission Vibration

[IdahoDave]

I have a 2007 Sierra Denali that I bought pre-owned with 11,000 miles. I have a vibration at 1500 rpm in all gears. It vibrates the floor, gas pedal steering column. I had it to the dealer and they said it was normal. The dealer installed (what they said was a dampner) that would lessen the vibration but would not take care of it. It had no effect. I sold Cadillacs for a couple years and sold well over 100 new Escalades that have the same 6.2 liter and 6 speed tranny and never had any of them with any vibration at all. Is this normal before they decide that they have a warranty issue and need to replace transmission? Any insight would be appreciated.

 

Thanks,