groho

Wow, never realized just how complicated this driveline angle thingy can get. Already have a 1" drop all around, with new suspension on my 66 coupe. Decided to do a shelby drop, right? When I got done, the front was sitting a little too low so I decided to pick up lower blocks to bring the back end down 1" also. During all this I remembered I had a nasty vibration in my backside with the new suspension, but it was smooth as silk with the old suspension. That vibration would go away at 70mph or so. I decided to check the driveline angle while I was under the car. Sure nuff, 3* down at the tranny, and .5-0* down at the pinion. I suspect the new suspension (stiffer leafs) was't allowing the pinion to come up under load to smooth out the ride. Then throw in the fact that you're lowering the car an addition 1" ontop of the what you've already done. Pinion up, pinion down? Remember opposing angles, right? Then CRS sets in (can't remember ****). End result, got the suspension and car sitting where I want, with 2.5* down at the tran, and 2.5* up at the pinion with 1* on the driveline. Fingers crossed, it'll work. The big question, WOT may force me to decrease the pinion a touch so it can wrap up, but I suspect that 4.5 leaf will limit the amount of pitch under WOT (stock 289)..... Am I on the right track? Sure the heck hope so. I think a new motor (331) will definately force me to look at this again.

67mustang302

By "up at the pinion" are you referring to that's how much angle the driveline has moving upward from the pinion? Did you use a pinion angle measuring tool?

Ideally, you want the driveline moving downward from the transmission, and upward away from the pinion. Typically the pinion will be pointing downward towards the ground, this evens the angles out and clears vibrations cruising, and gives the pinion room to move up under acceleration when the springs wrap up.

But you do NOT want a 0* difference between the driveline and either the trans or pinion, otherwise the needle bearings in the u-joints will brinell and the joint will fail.