SYE / DC driveshaft and pinion angle?

[bobthetj03]

So, I have an SYE / DC driveshaft, double adjustable rear uppers. I have the rear diff angle at 12.6* and the drive shaft tube angle at 13.7*. From other threads I've read, you want the pinion angle slightly lower than the drive shaft angle to account for torque load. Am I understanding this correctly? Also, when adjusting the angle with the double adjustable uppers, I checked the length of the arms as I adjusted but to keep them both identically the same length one arm tends to bind up. By that I mean I can turn one arm by hand to adjust, but the other tightens up to where I can't turn it by hand. If I free them both up to where I can spin them easily by hand the length is off by about 1/8" on one arm from the other. I assume you want to keep them unloaded to keep the arms from binding against each other? Anyway, does any of this make sense?

 

[Jerry Bransford]

It's ok to run the pinion shaft exactly the same angle as the driveshaft, or maybe a half-degree lower. That 1.1 degree difference you have now is maybe a little more than I'd run but...

There are several ways to adjust the pinion angle. Many use a bottle jack to lift and support the nose of the pumpkin (where the pinion shaft exits) to set and hold the desired pinion angle, then adjust the arms so they bolt in. Setting that pinion angle just a skosh high before adjusting the length of the control arms so they bolt up can help the pinion angle to rest at the skosh lower desired angle once the support of the bottle jack is removed.

 

[bobthetj03]

It's ok to run the pinion shaft exactly the same angle as the driveshaft, or maybe a half-degree lower. That 1.1 degree difference you have now is maybe a little more than I'd run but...

There are several ways to adjust the pinion angle. Many use a bottle jack to lift and support the nose of the pumpkin (where the pinion shaft exits) to set and hold the desired pinion angle, then adjust the arms so they bolt in. Setting that pinion angle just a skosh high before adjusting the length of the control arms so they bolt up can help the pinion angle to rest at the skosh lower desired angle once the support of the bottle jack is removed.

I have double adjustable arms, so I can loosen the jambnuts on the arms and lengthen/shorten to suit, but I get what you're saying about the bottle jack method. Yeah, I might raise it a 0.5* and see how it feels. What is your rule of thumb for the front drive shaft pinion angle? Mine is about 1.5* difference in the front.

 

[Jerry Bransford]

The front pinion angle requirement is the same as for the rear but it ends up being a compromise setting for sake of the caster angle. Set it for as much caster angle as possible without having so much excessive pinion angle that it causes vibrations while driving.

 

[bobthetj03]

What is a typical good caster angle for a 3" lift on 33's?

 

[Jerry Bransford]

What is a typical good caster angle for a 3" lift on 33's?

Edited, sorry I misread your question... A good caster angle for 33" tires would be 6 degrees, though just getting it close to that and no less than 5.5 degrees would be fine. 6 or better is ideal.

 

[bobthetj03]

Edited, sorry I misread your question... A good caster angle for 33" tires would be 6 degrees, though just getting it close to that and no less than 5.5 degrees would be fine. 6 or better is ideal.

Thanks @Jerry Bransford .