Thanks you for the input, I feel that I am. It going to be able to fix the problem my self. It sounds like I will have to find a driveline specialist with the proper tools and know how to get it fixed. I didn't know that the 157in wheel base with 3.73s are known for driveline problems.

 

I agree with Mike. The yoke on the rear looks low. My first thought, might be a crazy one, is well first they don't look like 4" blocks but the pic isn't clear to me. The blocks are tapered, are they installed correctly? The tapered end should be towards the front. Sorry if this is just me spewing nonsense, but I've had lifted trucks all my life. This is the smallest truck I've owned in 25 years I also run balance beads in my tires, no need to rebalance and zero chance of losing a weight off the wheel

 

no shame in asking for help from a specialist.

but before you do that get one of these:


Johnson Magnetic Angle Locator-700 - The Home Depot

and stick it on you pinion snout, then on your front drive shaft. shim your carrier bearing and/or rotate your pinion up (may need tapered shims) to get those angles as close as possible. don't forget to check your transmission angle as well. minimize the difference in angles across all the u joints. shim the transmission mount as needed.

worst possible outcome is that you solve nothing but gain a useful new tool for cheap.

best outcome, you save the time, hassle, and money it takes to hire a pro.

with regard to the driveline problems and the 157"wb trucks ... there is just a spooky correlation between the two. that's not to say that a truck with a 157" wb and 3.73gears is going to have a problem, it is just to say that when you hear of this problem it is often on a truck with 157"wb and 3.73 gears (and usually the ecoboost).

i wouldn't be surprised, though, if it is natural tendency for spring wrap exacerbated by the 4" blocks ... just my thoughts.

 

This is the same reason I'm not sure if I'm going to lift the new truck. I've got a 4.5" lift with 35's on my F-250 currently and it doesn't ride nearly as smooth as I would like it too. Makes me think once I get the F-150 lifting it with bigger tires is just gonna take me back to square 1.

 

Well the vibration is gone! had to get a custom one piece shaft, 5in diameter, 84 in long.

 

this is the first time i've heard of someone having a new driveshaft made to fix the shudder.

thanks for reporting back!
I'll file this one in the back of my memory banks for when it comes up again.

 

They should come with one piece shafts from factory if you ask me no doubt they would all drive smoother. ......leave it to an over thinker to muck up what should be simple (that's you engineers) ......go out on limb and design less vs more......by the way what'd that run you?? I recall a guy in the Superduty section doing the same and it was less than $300