[tooski]

I read lots of info on pinion angles.

1. Pinion should never be pointing up.

2. Pinion angle should be set to be equal and opposite to the trans output angle. If the output angle is 3* pointing down, then the pinion angle should be 3* pointing up.

3. For a leaf spring suspension, the pinion should be pointing 5-7* down.

4. For a leaf spring suspension, the pinion should be poining 5-7* down in relation to the output angle.
If the output angle is 3* down then the pinion should be pointing down 2-4*.

5. U-joint angles should be 1-3*, never 0*. No mention of relationship between output and pinion angle.

I'm in the process of welding spring mounts to the axle tubes.
Comments?

[Keith Seymore]

Looks about right. You are doing a leaf spring car, I take it?

Two comments:

a) What you want to do is address "U joint working angles". That's the inflection the U joint itself sees, and it is relative to the other components. Never the "ground" or the natural horizon (the car doesn't care where the ground is, only the other driveline components).

b) All of this measuring is done with the suspension loaded, not hanging.

I am also going to say something blasphemous but since I designed and developed drivelines for GM trucks I believe I can get away with it:

Zero U joint working angle would be ideal, from a torque standpoint, because it would minimize the torque transmission losses. The down side is that the rollers in the U joint cup would not move, thereby brinnelling the surface and causing a disturbance. That's why you want some "non zero" small angle....to keep those rollers moving. In the end, though - It's probably moot, since the leaf spring is going to allow the pinion nose to move up and down fairly wildly during use. If you ever have the opportunity to drive a leaf spring equipped pickup truck around with no box on it I would highly recommend it. It is very entertaining and provides some insights into this.

Basically you are trying to end up with some small, equal U joint working angles at the front and rear of the shaft, during load, and are putting some "Kentucky windage" in your static measurements in order to achieve that.

K

[jonmachota78]

Originally Posted by tooski

3. For a leaf spring suspension, the pinion should be pointing 5-7* down.

my understanding is 5-7 is good for drag racing. 3 deg is more appropriate for a street car. good question. ?

[Formulajones]

Originally Posted by jonmachota78

my understanding is 5-7 is good for drag racing. 3 deg is more appropriate for a street car. good question. ?

Depends.

The leaf spring suspensions move more under power, so the tendancy is to dial in more pinion angle to compensate.

Coil spring 4 link rear suspensions don't move all that much under power, so you tend to dial in less pinion angle.....with the idea behind these theories of having "zero" angle while accelerating down track = more HP to the wheels.

[68azbird]

For a regular type driver car with multi leafs 3-5 degrees with all the weight in the car as it will be driven.

[tooski]

Thanks Keith, excellent reading and instruction.

Originally Posted by 68azbird

For a regular type driver car with multi leafs 3-5 degrees with all the weight in the car as it will be driven.

So 68, would that be 3-5 degrees down from the trans output, or horizontal (car chassis)?

[Grand73Am]

What I've done is measure the pinion angle in relation to the mounting pads on the original rearend and duplicated that on the replacement rearend. For example, I've measured a 2nd gen Firebird rearend in the past. When the mounting pads were level, the pinion angle was 7* up on those rearends. So, buy duplicating that measurement on a replacement rearend, it works like the original one. This doesn't mean the pinion angle is 7* up when the rearend is installed in the car. It's only in relation to the mounting pads on the rearend being level.