1997 GMC Sierra torque-converter lockup issue

I have a 1997 GMC Sierra with a 5.7L V8. I am experiencin g a shudder when coming out of power when climbing a hill or coming out of a powered situation. It happens like clockwork when coming over the top of a hill. Once accelleration is applied it stops. 2 mechanics have referred to it as an issue with the torque-converter lockup. I have read a few comments online about a misfire causing this when at low rpm's, which is when this seems to happen. Any help would be greatly appreciated.

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It could be the torque convertor not coming out of lockup when it should (produces the same shudder as a 5-speed in 5th gear @ 25mph with yer' foot on the gas), or, more likely, a misfire being caused by a weak ignition component, exacerbated when under serious load.
If your TC was truly malfunctioning, you'd likely have DTC's stored in the PCM, as your transmission is electronic (4L60e) and controlled by the PCM.
When's the last time she had a major tune-up (plugs, wires, cap and rotor)?
Doc
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On Sat, 17 Apr 2004 00:17:40 -0400, "derekb007"
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    When's the last time you had the trans fluid and filter changed? Torque converter lockup clutches are sensitive to fluid quality, and can cause a shudder just as you describe. If it's more than 30,000 miles, get the old fluid out of there.