Rear end vibration

[VileZambonie]

Is the crossmember in direct contact with the frame or are the spacers between the frame and crossmember?

[K20Detroit]

Is the crossmember in direct contact with the frame or are the spacers between the frame and crossmember?

The cross member is in direct contact with the frame. Bolts are tight.
Got the new mounts, but have to get a bolt tonight for it

[K20Detroit]

Mounts are in, completely replaced them.
Transmission feels a lot better, maybe a 25% reduction in the vibration, but far from a cure.

Think i will take the blocks out next.

[VileZambonie]

Try putting the spacers between the crossmember and frame.

[K20Detroit]

Moved spacers, it's about 75% better.
I think the spacers might be too thick. Theyre about 1".
I will try measuring angles and use the spicer calc tool. I think a .5" spacer will be perfect.

[K20Detroit]

So here is what i have for measurements.
As it sat with the spacers between the crossmember and frame, it was 4d, 4d, 1u.
4 down on trans, 4 down on driveshaft,  1 up on pinion.
That means 0 degree angle on front joint, 3 degree on rear.
Took spacers out, ended up with 0, 6d, 1u.
That was 6 degree on first joint, 5 degree on second.
I played around with spacers and got it to 1d, 5d, 1u. So 4 degrees on both joints.

From what i have read, 3 degrees on all is considered perfect. However, it sounded like if you cant get 3 all around, it was best to get the pinion and trans synced.

[K20Detroit]

Update : brake drum was unbalanced. Replaced, smooth as glass until 70mph. Get a rear end vibe at that point. Did not happen on stands. Had it up to 90mph on stands with no vibration.