2004 Chevy Silverado shutter, shakes, rpm changes under lig

May have problem with the lock up torque convertor solenoid. At about that speed convertor clutch locks giving final drive ratio if there is a fault the convertor will engage and disengage causing shutter. press above the convertor stays locked below it 's diengaged

[quote:d686b74f5a="Docfixit"]May have problem with the lock up torque convertor solenoid. At about that speed convertor clutch locks giving final drive ratio if there is a fault the convertor will engage and disengage causing shutter. press above the convertor stays locked below it 's diengaged[/quote:d686b74f5a]

I appreciate your information very much. I have learned a lot about torque converters, auto transmissions and drive line componnents.
Turns out the rear Universal Joint was bad, the torque converter was locking up at speeds just over 40 mph, tapping the brake, the rpm increased about 250rpm and proved the torque converter released. When the vibration occured speeding up or slowing down got past the primary vibration of the U joint. Manually checking the U joint proved it to be the problem. Replacing both front and back U joints cost about $150.
Thanks you very much for your input, with a bit more research I am sure I saved literally thousands of dollars.

Good job U-joints that is one I will remember

Same symptoms with my Silverado (vibration - tap brakes/accel and goes away). Is solenoid the problem, or does torque converter need to be replaced?

Thanks!