I have Hotchkiss adjustable upper control arms on my 66. I just checked the angle at it is at a positive 1 degree. Should I go to negative 2* or try for a negative 5*? Thanks!!

It's 2 deg relative to the centerline of the driveshaft. Nose of the pinion down.

You need to determine what the motor/transmission is. It should be close to 4* down. If it's a street car that see's alot of miles you will want the rear end 3.5-4* up in order to keep the U joints in sync and not cuase vibration. If its doesnt see alot of street miles and vibration isnt a concern you might want like 1 or 2* up this way when you nut it and the pinion climbs the rear end angle should be parralel to the trani. angle.

As stated pinion angle is only for driveline alignment and has no effect on traction. I 2nd 2* neg (down)pinion no more for street strip coil sprung A- body. Leaf spring cars tend to require more as the pinion can clime more in a leaf spring car.

Take your driveline angle which, as already stated, should be between 3 and 4 degrees down towards the back of the car. measure this on your harmonic balancer, block, oil pan bolts or transmission pan bolts. Measure your pinion angle on the u-joint cap using a small socket that rests cleanly on the cap.

Next we have to establish how much power you are putting to the chassis or ground. Assumming your 12.95 netted you 106 mph (just a guess) and you weigh 180 pounds (just a guess) you are putting about 340 HP to the rear wheels or your motor is at about the 400 HP level.

At your output level, I would leave it at level (0) to -.5 degrees if your driveline angle is 3 down or at +1 if your driveline angle is -4.

I am putting 600 HP to the ground running 10.70's at 125 mph in a 3950 pound ride, my pinion angle is 4 1/2 (-3.5 down and -1 down) making a shallow "V"

So if I am at + 1 * now I should probably move my pinion angle to about a - 2 *, right? I do drive it on the street but not on long 2 hour trips. How does the rest of the driveline affect launch or what does it affect at all? Thanks for the info, though!!

Try this site for some good general info;

Pinion Angle (http://www.rosslertrans.com/tips/pinon.htm)

I'm still a little confused. I just checked my engine and it is at about a +5*. The trans is at about +3* and the driveshaft is at about +1*. The pinion is at +1*. Should I leave it or change it to -2*? I want it to be lined up for a good launch, ya know. So pinion angle has nothing to do with traction? I'm confused. :confused:

Originally posted by chevydog66:
I'm still a little confused.

I want it to be lined up for a good launch, ya know. So pinion angle has nothing to do with traction? I'm confused. :confused: I'm with ya bud.That's why I haven't even tried messing with angles... Yet smile.gif

Originally posted by chevydog66:
I'm still a little confused. I just checked my engine and it is at about a +5*. The trans is at about +3* and the driveshaft is at about +1*. The pinion is at +1*. Should I leave it or change it to -2*? I want it to be lined up for a good launch, ya know. So pinion angle has nothing to do with traction? I'm confused. :confused: Are you saying the Engine is higher in the back than in the front? In other words The driveshaft and the pinion form an "upside down V"

Yes, the engine probably sets a little higher than it should. I had to pry on the frame mounts a little to get the Moroso solid mounts to fit properly. I also plan on installing a driveshaft loop that mounts to the trans crossmember, which might change the angle as well. But right now the pinion angle is at +1*. In other words it is pointing up 1*. I put the adjustable Hotchkis uppers in at the stock length and have raced it that way. I am wanting to know if I should change it to a -2* or just leave it where it is? Thanks!!

No, the engine is higher in the front than it is in the back.

So if the engine is at 5 degrees pointing down, most likely the driveshaft is too. Leave your pinion at +1. That gives you a driveline angle of -4 making a shallow V. Please re-check that engine and driveshaft angle.

Make your upper control arm adjustments with all the weight on the tires. Use the left upper control arm to adjust the pinion angle after you attach the right upper and put in some pre-load. In your case just add maybe one turn of preload for starters.

The engine is pointing up in the front 3*. Is that a negative or positive? The driveshaft is pointing up in the front as well. The rear pinion is pointing up 1*. Is that negative or positive angle?

Take a look at the pic.

http://www.boomspeed.com/mc71454/pinion_pic.JPG

The First One is -3 to -4 The second one (the one you have) is -2

Exactly!! that is what I want to do. We were on the same page. But, how will it be beneficial to me? What all happens with the drivetrain at the line during a good holeshot?

During launch the rear will try to rotate up and in theory the driveline will become parallel, thus reducing friction.

You need to have some angle so the bearings in the U-joints rotate and keep lubricated.

You also need to be sure the driveshaft yoke can slide into the trans a bit. When the rear rotates up, it forces the yoke into the tailshaft. If it is already bottomed out in there, you will break stuff.

Originally posted by Epistuff:
You also need to be sure the driveshaft yoke can slide into the trans a bit. When the rear rotates up, it forces the yoke into the tailshaft. If it is already bottomed out in there, you will break stuff. Good point Jim..I believe the rule is 3/4" to 1" from bottoming out when the vehicle is at rest.