Need some help calculating pinion angle vs caster

[tscottg]

My D1 has OME 764 springs in the front and that is netting about 3-3.5" lift and I currently measure out at -2* Caster. I would rather purchase Caster Corrected Arms vs. the Re Drilled Swivel Balls. I also need to correct my pinion angle as it points too far up putting the front U joint in a 7* working angle and causing some vibes.
I have read that the optimum angle relation of DS to Pinion is 0-3* with a DC DS.

I currently have a fresh DC drive shaft not installed yet (rebuilt D2)
Stock front radius arms

Measurements are with D1 Single Cardan Drive Shaft

Pinion angle: 17*
Drive Shaft Angle: 10*
Caster: -2.0*

Given the calculations are for a SC DS those are the measurements. I have calculated a working angle at the pinion of 7*

Plan A: If I were to purchase the 3* Caster Corrected Arms I should move to -5* Caster and lower the working pinion angle to 6* (by lowering the pinion angle to 14* and thus lowering the DS angle to 8*)

Plan B: If I were to purchase the 6* Caster Corrected Arms I should move to -8* Caster and lower the pinion working angle to 5* (by lowering the pinion angle to 11* and thus lowering the DS angle to 5*)

Please help me decide which arms to buy. Plan B seems to be the best choice as it would gain the most caster and bring my working pinion angle 2* lower but please share your thoughts.

FYI im deciding between TerraFirma 3* TF508 or TerraFirma 6* TF528

Thanks
Scott

 

[p m]

How do you measure caster?

 

[Jake1996D1]

I am confused as hell by your post... You do or dont want to use that DC drive shaft?

If you use DC shaft make sure the pinion angle and DS are within 3* make sure you're measuring pinion correctly..

if you use conv. u joint make sure the pinion angle and transfercase are 3*

As far as castor correction.. fixing your balls is the way to go.. This way you keep the pinion pointing towards the t-case and will let you use the DC shaft effectively pending angles..

hope this helps..

 

[p m]

I am still interested in how caster angle was measured.
Stock height is 3 deg negative (top behind the bottom); radius arms are 52" long. Raising a truck 3.5" should make caster about 0.8 deg positive.

 

[tscottg]

How do you measure caster?

We did a caster sweep reading with a brand new Hunter Hawkeye alignment rack system.

 

[p m]

ok, that's good; what are your rear springs?

 

[p m]

I am still interested in how caster angle was measured.
Stock height is 3 deg negative (top behind the bottom); radius arms are 52" long. Raising a truck 3.5" should make caster about 0.8 deg positive.

Correction - what I called "negative" caster is normally called "positive." My bad.
So 3.5" of lift should make 0.8 deg of negative caster.

 

[Jimmy]

Yeah, I think the OP is getting negative caster and positive caster confused.

If the current reading is -2*, then the 6* correction arms will bring the caster back to near stock (3*, quoting the above). Now, this may not put the pinion where you want it (it will likely be too low/not optimum for a DC driveshaft, but livable).

As Jake said, the proper way to do this is get arms which will move the pinion to where you want it (dependent on which front driveshaft one wants to run), then install swivels which have been altered to give you the caster you need with the new arms. If you were really adventuresome, once could cut-n-turn the housing ends to adjust the caster but that's not as easily done on a LR housing as it is on others (Danas, Toyotas, etc.).

The 3* correction arms may get your pinion to where you want it for a DC driveshaft, but the caster will be less than perfect.

It comes down to what you're willing to live with, if you don't use both arms and adjusted swivels to correct both properly.

 

[tscottg]

Yeah, I think the OP is getting negative caster and positive caster confused.

If the current reading is -2*, then the 6* correction arms will bring the caster back to near stock (3*, quoting the above). Now, this may not put the pinion where you want it (it will likely be too low/not optimum for a DC driveshaft, but livable).

This is true.. I was thinking that negative was aft of the centerline when in fact positive is that.

So... 6* correction arms would bring me to roughly 3.5* positive (Stock Spec) from my current 2* negative.
Also Lowering the pinion angle to roughly 11* should put the u joint working angle at roughly 4*

Right now the pinion is basically pointed straight up... which sucks

 

[KyleT]

adjust the pinion to point at the t-case with arms, then get the balls machined to the correct caster.

why not the adjusted balls? it is way easier than toyotas who have to cut and turn. that SUCKS. i did it twice.