[sick472]

Well, when I was 18 I thought I knew it all, and at 52 I should know twice as much right?, but maybe not, lol. It turns out that the shudder was a product of a misfire in the engine. When the lock-up would occur in 4th gear...it was too much load on the engine (about 200hp) and caused the miss to exaggerate and it was actually the motor shuddering. Thankfully, a faulty sparkplug wire was the problem and not the solenoid, or worse, the torque converter. I am embarrassed that I did not notice the misfire myself, but thankfully my transmission guy picked it up during a test drive. To make matters even more embarrassing, some guy standing around the transmission shop, not knowing anything about my truck, out of nowhere from 20 feet away, says...that truck is misfiring! I'm a doof.

That's good news and I now have enough power to spin both tires which takes me back to 18 years old again. I'm happy and I THANK YOU PJ for teaching me a few things along this thread...I learned a lot!

The only downfall, minor albeit, is I really don't know how the transmission is actually wired internally regarding the available schematics. I am happy that it locks up in 4th only as lock up tends to lug even in 3rd and, lets face it, how much mileage can be saved during the short time that the truck spends in 3rd gear. Historically, the truck gets about 12 mpg.