Pinion Angle with Caltracs

[dvw]

The idea is to have the engine/trans centerline (C/L) parallel to the rear pinion C/L under acceleration. Pinion angle on any set-up first depends on the engine /trans angle. Then knowing what type of rear suspension you have. How far does the axle housing rotate upward under load? How far does the housing separate from the body during the run? Knowing these parameters you can set pinion angle correctly. Using the eng/trans angle you set the housing X number of degrees lower than this measurement. The X number depends on you suspension. In this case Calvert states 2 degrees. if the Eng/trans is down 2 degrees in the rear. You would set the housing to 0. If the eng/trans is 0 you would set the housing 2 degrees nose down. If the eng/trans were 4 degrees down in the rear you would set the housing 2 degrees up. Now you can see why knowing eng/trans C/L is necessary. The angle of the drive shaft is only a function of the distance between the the height/length of the engine trans C/L vs the height of the pinion C/L. In cars its not a concern. It can be a problem in a raised 4wd truck where there is a large distance. Pay no attention to driveshaft angle in this discussion. It means nothing. As far as springs. A S/S spring has a very stiff front half. The Caltrack bar is now the stiffing member between the housing and the frame. The spring now is only used to hold the car up. A lighter compressed spring has more stored energy than a stiff non compressed spring. That is why Caltracks will work better with the lightest spring. Unless we are talking big HP, like past 2000. Then the engine torque will apply the tire to hard. But that's another discussion.
Doug

 

[padam]

There's a lot going on here geometry wise.

It seems to me it depends not only on the angle of the pinion, but also the vertical distance from the trans center line.

 

[dvw]

There's a lot going on here geometry wise.

It seems to me it depends not only on the angle of the pinion, but also the vertical distance from the trans center line.

The vertical distance between the two C/L changes during the run. But it is a result of rear housing separation. You could have the two C/L a foot apart but still maintain the two centerlines parallel under load. That is what you are trying to achieve. Don't use the driveshaft angle in your calculation, it means nothing. You'll just confuse yourself. Look at these diagrams. They all have 2 degree pinion angle at static ride height. All 3 have different driveshaft angles.
Doug

 

[cdr]

dvw is spot on !!!!!! like I said on my car it likes 1 deg difference from the trans angle of 2.5 down, my pinion is 1.5 up

 

[padam]

Ok I'm starting to get it. The illustration helped a bunch, thanks.

Next questions;
Are you taking the measurement for each from level?
What's the best way to measure it?

 

[cdr]

as the car sits on the suspension, is how I do it, a drive on rack helps

 

[bm02tj]

this explains angles and why

 

[biomedtechguy]

this explains angles and why

I've seen this before. Very well done.

 

[padam]

as the car sits on the suspension, is how I do it, a drive on rack helps

I mean, what surface do you measure from?
Is the a surface on the trans, or diff that is parallel to the centerline?

 

[cdr]

I mean, what surface do you measure from?
Is the a surface on the trans, or diff that is parallel to the centerline?

I measure off the ujoint cap pointing down, the trans side of the yoke ujoint cap & the pinion yoke side, you can pull the driveshaft out & measure off the end of the trans output shaft & the machined face of the pinion yoke where the bolts go through

 

[383man]

The idea is to have the engine/trans centerline (C/L) parallel to the rear pinion C/L under acceleration. Pinion angle on any set-up first depends on the engine /trans angle. Then knowing what type of rear suspension you have. How far does the axle housing rotate upward under load? How far does the housing separate from the body during the run? Knowing these parameters you can set pinion angle correctly. Using the eng/trans angle you set the housing X number of degrees lower than this measurement. The X number depends on you suspension. In this case Calvert states 2 degrees. if the Eng/trans is down 2 degrees in the rear. You would set the housing to 0. If the eng/trans is 0 you would set the housing 2 degrees nose down. If the eng/trans were 4 degrees down in the rear you would set the housing 2 degrees up. Now you can see why knowing eng/trans C/L is necessary. The angle of the drive shaft is only a function of the distance between the the height/length of the engine trans C/L vs the height of the pinion C/L. In cars its not a concern. It can be a problem in a raised 4wd truck where there is a large distance. Pay no attention to driveshaft angle in this discussion. It means nothing. As far as springs. A S/S spring has a very stiff front half. The Caltrack bar is now the stiffing member between the housing and the frame. The spring now is only used to hold the car up. A lighter compressed spring has more stored energy than a stiff non compressed spring. That is why Caltracks will work better with the lightest spring. Unless we are talking big HP, like past 2000. Then the engine torque will apply the tire to hard. But that's another discussion.
Doug

Yes Doug (DVW) is dead on so listen to this info he posted. Ron