Hi all - asking for some advice / opinions. I have a '98 1500 with the 5.7, 4x4 / 4L60E, and ~200K on the ODO.
Recently, it's been shaking under load in overdrive. It's worst if I'm going up a hill and give it some gas to maintain speed - it will shake unless I let off the gas or give it enough for it to downshift. I've tried stepping on the brake slightly while it's shaking (to test TC lockup) and the shaking does not stop. I towed a small trailer recently, and the shaking was exacerbated (happening with any amount of acceleration in OD).
Engine has ~60K miles on it and trans was replaced ~3 years ago with an unknown mileage unit, but has been solid since. Do you suspect a trans issue? Maybe u-joints? I put a tube of ShudderFix in with no change (generally not a fan of magic solutions, but figured why not try). No codes / lights on dash. Any ideas would be appreciated, thanks!