'99 4X4, 5.9L Torque converter shudder
I have a '99 Durago 4x4, 5.9L with about 93K miles. Over the past year I've experienced a loss of power, particularly when its in overdrive on the expressway. Even at 60-70mph, the slightest incline causes it to shift into passing gear. More recently, I've noticed a sputtering under these conditions (not noticed before). It is even apparent now when driving at ~45mph and it goes into overdrive - runs about 1200-1500 RPM at this speed. When I turn off the OD, it still 'shudders' when under slight load.
I've done some research on "torque converter shuddering" and have talked to folks who experience similar conditions on GM SUVs. I have run across a small tube of lubricant that is supposed to fix this condition. But, I am VERY skeptical on any quick fixes.
Trannny fluid hasn't been changed in awhile, so I thought that'd be first step. Anyone input would be appreciated!