Technical Pinion Angle with Leaf Springs

I've searched both here and abroad and can't find an answer to this. I'm about to weld leaf spring perches to my new axle housing in my '64 F100. My understanding is that with leaf springs, you are supposed to factor in some amount of additional negative angle at your pinion to account for leaf spring axle wrap under acceleration/load. Problem is, 99% of what I've read seems to be meant for racing applications. They say to add as much as 4-5° beyond what would otherwise make your pinion angle perfect. I can understand that much extra angle to be right in racing environments where you're launching hard, but what about for more casual street use? How much is right when you're really just cruising at constant speeds most of the time?

In other words, right now my trans-to-driveshaft angle is 2° positive. Should I set up the pinion to be 2° negative (which would make for perfect u-joint harmonics under no load) or do I go 3° or 4° or more to account for axle wrap? I just can't decide how much additional angle is right for this truck's intended purpose (all street, occasional light towing, no launches).

Gurus please chime in!

 

Just make it the same as the back of the trans ...

 

When I install rear parallel leafs I normally set the pinion to be neutral — tack the brackets and then load the vehicle to see how it sets. If need be, I can remove tacks and rotate to desired angle. Most of my builds usually are set at 3 - 4 degrees negative.

 

How often are you going to wrap up the axle?

 

Almost never. Don't really have the power for it anyway. Will be running probably less than 300hp. Thinking I'll just add 1°.

 

There's a video here with modified rear leafs to lower the truck. Many leaves removed and the rear spring wraps close to 20*. (+10 and -10 from static) nothing is gonna help there.

Set it at neutral angle equal to Trans.
If it needs a tweak there are angled shims.

 

Transmission = 3 degrees downward
Rear end = 3 degrees upward (parallel to the transmission angle)

- EM

 

Okay so the consensus is to not worry about leaf spring wrap and just set up both trans and pinion neutral (parallel) to each other.

Thanks for the feedback guys.

 

Yup.