[robnolimit]

Lots of thread postings lately discussing the mounting point of trailing arms. The hieght of the pivit mount determines the "rate of rise" or "anti-squat" transfered to the rear tires. There is some disussion on wheather to raise or lower the pivit point for better handling/traction... This also may effect pinion angle, So, lets have a look.
Pinion angle If you are working on a truck with an existing rear axle, (most are) and it is stock height, then the pinion angle is set to factory spec. If you lower the truck 4", the pinion angle will decrease appx 3 deg. Raising the front pivit point of the trailing arm 4" will restore the pinion angle to it's orig. spec. As a note, It would be ideal for the pinion to be parallel to the crank/trans center line.
Anti-Squat Is heigher better? - maybe. It's all a trade off. lets start with some basic driving info. If a car/truck has "Oversteer", then when you go through a turn, the front will turn in, and the rear may tend to get a bit loose and rotate out, loosing traction. The truck is turned MORE than the input from the steering, = "Oversteer", or "LOOSE". Now, if the car/truck has "Understeer", then, when you turn the wheels in, the truck will not respond as quickly. The rear has great traction, and "PUSHES" the front straight. In this instance, the truck turns LESS than the steering input. It has "UNDERSTEER", or a "PUSH". Somewhere in th middle is a balance. If we take the front suspension out of the equation for a moment, to see how the rear can effect steering, we could say this. - More traction = push. Less traction = Loose. more traction is better, right? Maybe not if your in a corner. If you aretrying to get through a corner at speed, and the front "pushes" you have no choice but to get off the throttle, on the brake, and slow down enough to get the truck to turn. This is the slow way around. If the truck is "loose", you can use the throttle to help steer through the corner, as long as your not to heavy footed.
So, back to production based Chevys. Most trucks push a lot if you drive them hard. The weight imbalance (nose heavy) tends to make then "push" into a corner, and get "loose" on the way out. Since it is easier to drive with a bit of a loose condition, and most of us are dealing with existing axle housings, I tend to recomend raising the pivit point. Now, if it was a truck mostly for drag/straight line fun, then I would leave it low, and use a wedge shim to fix the pinion angle. Some companies, like Hotchkis, have a front trailing arm mount with multiple mount points. Realisticaly, you would need to check the pinion angle at each setting to get a true comparison. Also, Horsepower comes into the discussion. As we add Hp, traction goes away, So it is fair to say that a truck with big Hp may benefit from a slightly lower pivit point. On our "Silver Bullit", we have moved the front many times. The goal is to have as much traction as we can get, up to the point that it has a push, then we back off a bit, keeping it just to the loose side.