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That's a good point to measure from, that flat is precisely perpendicular to the pinion angle.
 

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Discussion Starter · #3 ·
That's a good point to measure from, that flat is precisely perpendicular to the pinion angle.
Jerry

What is the preferred pinion angle for 3in SL with 33s? I've started getting some wandering over 60 MPH and also noticed last night my steering wheel doesn't return to center on its own after making turns. Everything I've been reading on here recommends making sure the caster and pinion angle are correct first before looking any further. Thanks
 

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There is no preferred pinion angle, it varies according to the configuration. Pinion angle takes precedence but the normal way to set the caster angle up is to dial in as much caster angle as possible before the pinion angle becomes excessive and starts vibrating, then back the caster angle off a tad until the vibes are completely gone.
 

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Jerry

What is the preferred pinion angle for 3in SL with 33s? I've started getting some wandering over 60 MPH and also noticed last night my steering wheel doesn't return to center on its own after making turns. Everything I've been reading on here recommends making sure the caster and pinion angle are correct first before looking any further. Thanks
Pinion/caster angle (in degrees) cannot really be measured with an angle finder unless your Jeep is sitting on a perfectly level plane (like an alignment rack). A few degrees of slope that a typical garage floor has will throw that angle off by that much.

Get as much caster as you can without causing driveline vibes.

A good way to go, is to once you get it set up, take it to an alignment shop and get a print out of what it is. you can then use those numbers for a base line and subtract or add angle changes to that base line.
 

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Discussion Starter · #7 ·
Pinion/caster angle (in degrees) cannot really be measured with an angle finder unless your Jeep is sitting on a perfectly level plane (like an alignment rack). A few degrees of slope that a typical garage floor has will throw that angle off by that much.

Get as much caster as you can without causing driveline vibes.

A good way to go, is to once you get it set up, take it to an alignment shop and get a print out of what it is. you can then use those numbers for a base line and subtract or add angle changes to that base line.

If I were to get an HP30 I'm assuming I could keep a better caster angle because the pinion angle wouldn't have as great of an affect on the drive shaft angle right?
 

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Except I read somewhere that as built the HP has less angle between ball joint axis and pinion axis so an HP gets less caster angle for same pinion angle by a couple or 3 degrees
 

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I was worried about loosing even more caster angle after my 4" lift and tummy tuck. I was especially concerned because we flat tow our Jeep behind our RV and the more caster, the better it tracks. I went to an HP30 for mainly that reason and was able to get caster numbers up over 6 degrees.
 

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Since the correct pinion angle would indeed be about 3 degrees different between a HP and LP axle, I'm believing that chart isn't saying you would get 3 degrees less caster angle by converting from LP to HP.

Jeep knows the optimal caster angle is approximately 6-7 degrees and they're not going to not set the HP's inner C's so you couldn't obtain that optimal caster angle. That Water Dog got 6 degrees of caster angle with his HP D30 seems to indicate exactly that.
 

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I read it as since with the HP stock they need less pinion up angle they weld the axle housing with three degrees less angle difference between ball joint axis and the axis perpendicular to the pinion axis so it is a wash

You need about 3 degrees less up angle of pinion for driveshaft alignment with the HP replacing LP but it nets you no caster as there is three degrees less caster built into the HP for any given pinion angle

At least that is how I read it and on a CAD overlay diagram I saw with both axles at same pinion angle (horizontal) the HP has three degrees less caster angle
 

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Gotcha, it looks like we're saying the same thing. With either axle, LP or HP, you end up with the same optimal Caster angle.
 
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