... and it works!

Did the install on my own, and because this is my first Hot Rod, sometimes i get worried when im 'big tasks' on my own, so when im finished and the chit works like its supposed to, i get jazzed.

Anyway, the 2.73 gears are NO MORE! Now this week i gotta pick up some Hoosier Quick Time Pro slicks, 15 x 10 x 28", then trailer it down to Maple Grove 1/4 imi. in Penn State next weekend and see if i can get in the 11's !

Hey, anyone got any sure fire ways of finding "true" pinion angle other than eyeballing it?

I got S&W sub-frame connectors with adjustable torque arm. Can seemy website for pics.

 

Pinion angle is the difference between the angle of the driveshaft and the angle of the pinion.

I put my car up on jack stands under the axle. Since the pinion angle has nothing to do with the angle of the ground, the wheels don't have to be on the ground but the suspension can't be unloaded (hanging).

Use an angle finder. Hardware stores should carry them. I have one with a magnetic base.

Put the angle finder on the driveshaft and get the angle. It may be 3*. Since you're using a torque arm I assume it's a bolt-in diff. Put the angle finder on the torque arm mounting pad since it should be on the same plane as the pinion.

If it's not a direct bolt-in and you don't have a torque arm mount you'll need to drop the driveshaft now. Put the angle finder on the yoke. It's 90* off the pinion so you might get 92*. Subtract the 90* to get 2* pinion angle.

Add that to the driveshaft angle and you have 5* pinion angle in relation to the driveshaft. Just be aware of positive and negative angles. If the angle is zero then the driveshaft is directly in line with the pinion. going to 5* down angle would be like pushing the yoke down 2 1/2* from that point.

 

Steve, are you sure about that? I have read, and was always under the assumption that pinion angle was relative to ENGINE angle...not the driveshaft.

Engine angle and pinion angle should be parallel to each other. A slight negative (1-2*) pinion angle setting will pre-load the suspension so that under power, the pinion would rotate up and be back in alignment with the engine. The ideal drag racing setup would be where everything is in line (engine, driveshaft, pinion), however on production vehicles, the engine sits at a 3* angle (down towards the rear) for engine compartment clearance. That is also why carb intake manifolds have a built in "wedge" so that the carb can sit level.

Stock suspensions are supposedly designed with 0* pinion angle, relative to engine/trans angle. Adding aftermarket rear suspension parts which change the ride height of the vehicle (springs, bushings, shocks, LCA brackets, etc.) are what necessitates the use of a torque arm to correct the pinion angle.

 

Yes I'm sure and both angles can be changed. The diff pinion angle is easy to change once you have the adjustable torque arm. The angle between the transmission output yoke and the driveshaft should be zero. This means you need to raise or lower the rear of the transmission.

The straighter the angles are the less driveline vibration there is. This vibration is caused by the u-joint slowing down and speeding up as it rotates or wobbles around at an odd angle.

The diff pinion angle will always change when under accelleration or decelleration. A factory setting of zero is a middle of the road compromise. By setting it to a few degrees down, negative, you'll wear out the u-joint a little quicker but under hard acceleration when the diff rotates upward, the u-joint will be at zero angle and can transmit torque with no binding of the u-joint.

If you also look at the engine and tranny you'll see that they are not in the center of the vehicle. They both sit towards the passenger side. This is to allow the steering column to go past the engine. Since both are off center the pinion is also off center to compensate. The driveshaft does not go down the center of the car. When I installed my 9", the pinion is 2" farther to the passenger side. This creates another angle. From simple trigonometry I've found that my offset angle is 2.63*. This gets compounded if the pinion angle becomes excessive. So far I don't feel any vibration but then the car is only under power for less than 12 seconds.