ChucksCL-S

Slowly I have developed a shutter when giving the car a little gas, usually up hill around 55 or 60 mph. It is annoying. I have a recently replaced tranny that made no difference before or after, balanced the tires, new axles too. I even put on my snow tires to see if that made any difference, none. Still there. I noticed if I use D4 up to 65 and then shift into D5 I avoid the problem for the most part. Motor mounts are good too. I'm am lowered an inch or so and have Ingalls kits all around, and a recent 4 wheel alignment. Car runs perfectly in all other respects. Any ideas out there? Thanks