It's a 4L80e with a VAS fab crossmember.

 

Do you know what the factory transmission angle should be? How much did you shim your trans in inches?

 

ok i just looked true your pics and see what your saying, your drive shaft angles up as it exits out of the trans so you need to be like that last pic but the diff on left side and trans on the right

it kinda looks like you need to lower your trans to help you get the angles right

 

I really don't feel like we are on the same page here man, lowering the tranny would make the angles even worse. Raising the tailshaft is the only thing that will lessen the operating angles of the u joints.

Those numbers in my drawing today were just hypothetical numbers. Right now my tranny is 6.1 degrees and the rear end is 2.7 degrees without any shims. I added a 3 degree shim, so now it's 6.1 degree on trans and 5.7 degree on diff, which makes them very close to parallel, but the vibration is still very violent.

 

them being that close and it being violent either your off on your numbers or you are making contact with something

 

I believe it's because the u joints are operating at around 7.5 degrees when they apparently should be 1-3 degrees. Definitely not contacting anything or I would surely see damage on the driveshaft.

 

so i been thinking about this...

i do think you should raise your trans up at the rear if it needs a few inches or more (if you can ) some square tubing would work, the reason i say that is my truck right now lowered same as yours but i did a shock relocation kit so right now under hard acceleration and @WOT shifts im getting a vibration due to axle wrap not sure if its the u joint or the driveshaft is making contact with something under the truck (think its the driveshaft have not had time to check) but with that said if you angle the nose of your diff up your going to make the drive shaft closer to the cab and cross supports and that might be a problem if you load, tow or even hitting bumps so if your able to raise the rear of the trans and get the drive shaft nose down at the axle side get the angles right that would be your best bet

 

I'm putting a 04 silverado 1500 rcsb together and it has a returnless fuel system. how did you setup your system? So far I plan on using the DW400 fuel pump module .

 

This build is fire! Reminds me of my turbo 6.0 but 100x cleaner! Lol