Pulsation felt in gas pedal

I just purchased from a dealer, a 2006 Trail Blazer, 4WD, LS w/ 4 speed automatic transmission. I feel a pulsation coming from the gas pedal. It happens when I'm going 68-70 mph, then back off to 60 mph, then slowly re-accelarate back to 62-65 mph. At that time there appears to be a shifting action taking place. I can feel this pulatation or vibration through the accelarator pedal. It is not a harsh feeling. You have to be travelling on a smooth highway inorder to feel it but it is there and it hangs around for a bit. It does not just shift, then disappear. It actually feels like metal rubbing on metal. It does not sound normal.

I do have an appointment with a dealer tomorrow but would like to get a few thoughts from this group before I go up there.

Any insight on this condition would be appreciated.
Thanks

This a problem with many of the TBs. Try lightly to apply the brake pedal with your left foot. This will cause the torque convertor clutch to release. Do this test when the vibration happens, keep your right foot on the gas pedal. GM has rear springs that help with this problem but it is not a cure. Please let us know if there is a cure.

That vehicle has a drive by wire setup. The pulsation is probably just do to normal vibrations in the vehicle. The rear springs bulletin is for a noise in the rear end over bumps and does not sound like it will apply in this situation. I dont think there is anything wrong with you car.

Actually guys, the rear springs have been replaced to dampen a drivetrain harmonic shudder at 55-62 mph with the 3.42 diff, this was a common issue in the 2002-2003 TB. It is a growl or hum/vibration felt in the pedal and floor at those speeds, the springs are made of a different composition to dampen most of it out.

I just purchased from a dealer, a 2006 Trail Blazer, 4WD, LS w/ 4 speed automatic transmission. I feel a pulsation coming from the gas pedal. It happens when I'm going 68-70 mph, then back off to 60 mph, then slowly re-accelarate back to 62-65 mph. At that time there appears to be a shifting action taking place. I can feel this pulatation or vibration through the accelarator pedal. It is not a harsh feeling. You have to be travelling on a smooth highway inorder to feel it but it is there and it hangs around for a bit. It does not just shift, then disappear. It actually feels like metal rubbing on metal. It does not sound normal.

I do have an appointment with a dealer tomorrow but would like to get a few thoughts from this group before I go up there.

Any insight on this condition would be appreciated.
Thanks

I did take my TB to the dealer. The pulsating that I felt in the gas pedal is the torque convertor as suggested by maxwedge. It's inherent in the system. I drove another 2006 that they has on the lot and felt the same thing. I can live with this. My concern was that the pulsating was the sign of a transmission problem; it is not.