I don't think we are on the same page here. The trans always points down, even in stock application, and the diff points up. If I point the nose of the diff down I would have nowhere near what any of the driveline experts recommend. I have a flip kit on the truck, so what you're referencing is for trucks that have shackles, hangers, etc.. Flip kit trucks react opposite because the axle is on top of the spring. In a flip kit truck, the fat end forward makes the pinion face up, but in a stock truck, the fat end forward will make the pinion point down.

At this point I understand what needs to be done and I think shimming the tranny is the only way. 8° working angle on the front joint is too extreme.

 

The truck I had the vibration with was a 04 Rcsb with a flip kit, I’m not sure what your watching or reading? But we are not on the same page agreed

installing the flip you lessened the drive shaft angle so if you put the shims in the right way you add to the drive shaft angle

 

Spicer, Mark Williams, Tremec, etc... They all say to have the trans and diff at equal angles to each other with a 1pc driveshaft, like the picture below:


In my case the trans points down at 6 degrees, so I bought shims to point the rear end up to the same 6 degrees like the above referenced picture. Come to find out, anything over 3 degrees for a u joint can cause vibration, even though I watched a spicer video that said u joints like to operate between 5-8 degrees. After I saw that I chose to shim the pinion up to match the trans. At this point I think I need to raise the trans as high as possible to get an angle better than 6 degrees downward. I don't know what factory angle is, but it could be the VAS mount I'm using isn't worth a damn and lowered the trans mounting height causing the high angle.

 

i hope this helps (im not a very good drawer lol)

this is what i mean by you made the angle less when you installed the flip kit



now the rear of the trans height and the front of the diff height are different you dont want them pointing at each other (one can be 14 inches off the ground and the other 24 inches) just using numbers, you just want them close as you can get them to the same degree angle (watch the vid i posted) look at a truck with a 6 inch lift the diff and trans are not pointing at each other they are just at or close to the same degree's even tough there might be 10 inch difference in height

so to get what ever your truck needs to correct the angles you need to play around and find out, as i said i had to raise the trans up and angle the nose of the diff down i dont see why your truck would be any different only thing that maybe different is the shims and spacers you need but other wise its the same

 

If the trans is pointing down, and I made the diff point down as well like you're suggesting, wouldn't that make it like the bottom picture? I would no longer have angles that are in line with each other. They would be crossing planes at that point.

In my truck, the rear diff is higher than the output shaft of the tranny.

 

you shim the trans get the back of it up, angle the diff down so its like the second one from the top showing in that pic

when you installed the flip kit brackets they have an offset hole, did you put the offset facing the cab side or rear bumper?

 

So are you saying to do it like the bottom picture instead of the top?

 

this is what your shooting for




so i had to shim the rear of the trans up some then install the shims under the diff so it lowered the front of it (pitched it down some)

do you remember about the offset hole in the bracket? im wondering if you installed it wrong?

 

The differential is higher than the tranny, so I don't see how that drawing will ever be attainable in a flip kit truck. Or are you saying the left side of that picture is the differential?

Even jacking the tranny up so far that the mounting stud was completely out of the crossmember didn't net me anything more than a degree or so.

The flip kit is installed correctly per McGaughy's instructions. I believe the hole is towards the front of the truck which pushes the axle backwards to stay centered in the wheel well. The flip kit saddle itself is the same height on each side, so aside from the axle orientation in the wheel opening, it doesn't change the angle of the pinion.

 

i was thinking the LEFT side was the trans and right side the diff

are you stock 4l60e or was the truck swapped and the crossmember modded or replaced?