T5, TCP suspension and pinion angle 1966 coupe

[clone]

I have read a lot about pinion angles and I think I get it, but I dont know what to do. I checked my engine/transmission angle at the crank by measuring at the balancer and recorded 0*. My driveshaft also recorded 0* and my rear end showed 0*. So to me it seems very level with the ground, which I dont think is good. I have the full TCP suspension, front, rear, subframe, etc. My car is low, but is about as high as I can get it, but it is also level with the ground. So, I am only trying to address this because I have a bad vibration at around 80mph. I can easily twist my rear end to change that angle only. I cannot really raise the rear of the car any more, and lowering it would also be a challenge because the front would have to be lowered to match ride height and I dont think it will help. I thought it is ideal to have the rear and tranny on the same angle, which for me is currently 0*. I also cannot really raise or lower my transmission much, maybe could raise it an inch. So I am looking for some expert advise on fixing the vibration, which I believe is a drive line issue. The easiest thing I can do is lengthen or shorten the torque arm which would twist the rear end and change that angle. Unsure if it would change the driveshaft angle though. All help, suggestions, experience much appreciated. Thanks

PS this is a 289 with a T5, 9inch Fab9 rear

[GT289]

I seriously doubt having zero from front to rear is the source of the vibration.
You'd want some angle at the trans end and at the rear you'd want
the exact opposite angle. (Down at the trans and up at the pinion)
Maybe 2.5 degrees or so....

You can chase this kind of stuff for awhile trying to figure it out. Here's a
chart.

[GT289]

It's kinda funky that it comes in at 80 mph....

[clone]

Thanks for the response and chart. I am thinking I might try to replace the u-joints and have it checked for balance and run out. I noticed it is rusty, maybe its like uneven rust causing an imbalance? as that should be quick and "easy" and take it from there. Then I might have a 'pro' look at it hahah

[clone]

Just a follow up for anyone looking, my driveshaft was out of balance, and the most likely culprit was missing needles in my u-joint at the pumpkin! my wheels were also out of balance, problem is much better basically resolved!

[ScottsGT]

I was also going to suggest having the drive shaft ends checked to make sure the bearing caps are still tight in them. I just had my driveshaft shortened and the shop discovered my weld on yoke was worn out. You could spin the bearing caps with ease.
Apparently this is an issue with the original style u joints in the mustangs.