Okay, I know the formula and everything for setting the torque arm, but I need to know which way is positive and which way is negative in relation to the car. Thanks.

 

Imagine what would happen if the rear end pointed straight at the back of the trans.... the rear U-joint would hardly be necessary. That's what you're looking for; such that when the rear end torques slightly during acceleration, it will point itself straight that way.

You want to set it so that the rear end points about 1-1½° below straight at the trans. That would be considered "negative" I guess.

 

So the positive/negative measurement is related to the horizon? Negative = below, positive = above? Just curious...

 

I suppose you could say, it's with respect to horizontal; but it's the difference between the rear end angle and the drive shaft angle. You want the rear to be less angle off of horiz than the DS. The DS might be at around 4° or something; so you'd want the rear to be at 2½° or so.

I use one of those cheap angle finders you can get at Sears; with a little care, it's plenty accurate enough.

This needs to be done with the car sitting in its normal attitude with the weight on the rear wheels, so you need ramps (for the rear at least), or a pit, or a drive-on lift.