To clarify, my shudder is not the 55 mph wobble, nor the low speed 15-20 mph shudder. Mine occurred from a dead stop, during the first 4-5 feet of travel, and it pulsed/ shuddered 3-4 times, from every stop. It was more noticeable, with more aggressive launches, but always there, and always annoying. I always felt like a clutch pack in the trans was bad, or the torque converter was bad. Although it was a subtle annoyance that my wife never could feel, I never felt that before in any vehicle I have driven, and I couldn't help but wonder if something would prematurely wear, as a result.
Reading countless threads, some related and some not, to my particular issue, I surmised it MUST be due to axle wrap. I had read where others had success with adding 1" bump stops on each end of the helper leaf springs, in place of the flat factory insulators.
Not wanting to waste money in a fix that may not work, I came up with a no cost way to check its effectiveness. I had some scrap 3/4" PVC pipe (it is 1" O.D.) and some zip ties on hand. I cut two pieces 3" long, the same as the width of the leaf springs, and climbed under the the truck with some zip ties and a pair of side cuts.
I wedged the PVC in between the helper and other springs, just as it became snug, behind the factory rubber insulator. Then I wrapped a zip tie through it and around the helper spring, to hold it in place for the test. I only did this on each side, at the front of the springs for the test. A more permanent shimming of the springs would probably be best done at front AND rear, of each leaf spring. But, just doing the front, would suffice to prove whether axle wrap was causing my pulsing acceleration.
Well, after putting the PVC in there, I took it for a drive to pick up my son at school....NO MORE PULSING ACCELERATION FROM TAKE OFF!!! No matter how hard I took off, I couldn't get it to shudder! I was thrilled, to finally have it figured it out, and now know that it is not an issue with the transmission!
I know this is not a permanent fix, but at least I know what it takes to stop it. I plan to buy a set of hard urathane bump stops, at about 1 1/8" tall, to bolt in there.
Here are some pics: