So I installed my Jegster adj. torque arm this weekend and I'm not sure if I set the pinion angle the correct way.

I went to ACE hardware and got a magnetic protractor for 10 bucks.

First I put the angle finder on the bottom of the flat torque arm plate. It read .5 degrees positive. Then when I put the angle finder on the drive shaft, I got like 2 degrees negative.

Now, I know that cars are not the same as Math so .5 degrees positive plus -2 degrees does not equal -1.5 degrees.

So I adjusted the angle until it read a positive 2.5 degrees. That should equal 2 degrees of negative pinion angle.

Now when I say I read a certain number on the protractor as negative or positive, I mean that the protractor has zeros on it, and when I had it on the plate and on the drivshaft, the readings were either above or below the closest zero, but hardly at all, that's why it was a biznatch to figure out.

For those of you who have done this before, please help me out. Did I do this correctly???

The suspension was loaded and I followed directions, but I don't know if I read the angles and did the math correctly.

Thanks in Advance guys,

Peace, Matt

 

You're adding the angles, where you should be subtracting them. Here's a write-up, since some of this is a bit visual...

http://www.go-fast.org/z28/pinionangle.html

Dave

 

No, I subtracted them. I subtracted the angle of the driveshaft from the angle of the torque arm bottom plate.

 

That's why I pointed you to the link, to verify what you did.

You state above: 0.5 + (-2) = -1.5

That's adding them, not subtracting them.

Dave

 

Doesn't a Jegster torque arm come with instructions?
Instructions from Spohn for adjusting pinion angle:
Using an angle finder, place it on the driveshaft and record the angle indicated.
Next, place the angle finder on the flat surface where the torque arm mounts to the rear end (this surface is parallel with the pinion shaft) and record rthe angle indicated.
Subtract the pinion angle from the driveshaft angle. The result is "true pinion angle"
In order to apply preload you need negative pinion angle. Adjust the torque arm so that the front of the pinion goes down; continue to check each angle until the pinion angle is more degrees down than the driveshaft angle.

 

my BMR torque arm cam with angle finder and directions

 

Nope.

 

Yeah, with the #s you provided, your looking at -2.5. Math with negative & positive angles are a sumbitch.

 

So you guys are saying that reading pinion angles is just like algebra huh?

I don't really see how that can be accurate. If I have .5 of positive angle and then SUBTRACT -2 degrees, you will not come up with -2.5 degrees. It make plenty of sense algebraically but not in the real world. Where does the extra degree come from???

It makes more sense to simply take the negative 2 degrees away from the .5 degrees to come up with -1.5.

Maybe this does not make sense to you guys, but that is the way I see it. I'll call Spohn today and see what he says.

 

Anyway, i did it backwards. I subtracted the driveshaft angle form the pinion angle when it is supposed to be the other way around.

You are supposed to subtract the pinion angle form the driveshaft angle right???

So it would be -2 minus .5 which would equal -2.5 also.

Can somebody tell me how these different equations LOGICALLY give me the same pinion angle, when it seems to me this is inaccurate.

I'm no idiot and have done my fair share of algebra, but sometimes it doesn't seem to work in the real world like it does on paper.

 

Well, not to get into an algebra/geometry tangent, but when you are subtracting negative numbers, you're actually adding that number's inverse (positive).

Subtracting a negative # (i.e. -2*) from a positive (0.5*) is like saying 2+0.5. When you do it the other way around and subtract a positive # (0.5) from a negative (-2.0), you are taking a positive value away from a negative, increasing the negative #. I think you're just missing the negative/positive part of the equation.

(-2*) - 0.5* = (-2.5*)
0.5* - (-2*) = 2.5*

Hell, I came one test away from failing algebra in high school. All the formulas never made sense, but when I can see it in real life and visualize it...different story.

 

I just called Spohn and got it over with. He told me that because of the type of angle I am using, same kind he uses, it depends on which side of the car you are on to determine what is positive and negative. In other words which side of the zero it is falling on.

So I just jacked the rear of the car up, and using his formuls found that I had it set to -2.5. The driveshaft read 6 degrees and the pinion read 8.5 degrees. It was much easier to read the angles with just the rear jacked up.

So I set it to about -1.75. I just wanted to be within -1.5 and -2.

Thanks for the help guys, I finally got it straightened out and it's hooking pretty good. It was hooking a bit better at -2.5 degrees but I was loosing too much power through the drivetrain and could feel it a little bit up top. Now it feels just right.