Nine Inch Pinion Angle

9" sense

First - pinion should never point down. If you're having that much axlewrap that you have to compensate for it by turning it down, you need a traction aid, else you'll bend your springs into a 'W' (been there, done that) 9" will oil just fine pointed up around 5*, so don't let that be an issue with setting the perches. It sounds like the numbskull that welded in your perches put them on 2.5* the wrong direction. They owe you a proper installation, talk to them about taking it to another shop, and having new perches (no torch and move) welded in the correct place. Your pinion should compliment the angle of the driveshaft. Get it fixed now, or you'll break the yoke and tear up a bunch of u-joints unnecessarily. If you're gonna pay that much for a new axle, make sure that it's right 100%.

PS - new spring perches for a 9" should run about $12 ea.

PPS - if you're turning enough torque to warrant a 9", you may want to look into a traction aid. Ladder bar with a subframe connector, 3 link, 4 link, etc. The little springs on a 'Stang will be wrapped up in no time, once you apply that torque to the ground.

Will the pinion angle remain the same in a 3 link, 4 link, and ladder bar setup?

Mustang67Coupe said:

Will the pinion angle remain the same in a 3 link, 4 link, and ladder bar setup?

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Yes. It will never move.

The corny traction bars that were so 'rad' in the 80's on every mullet sporting camaro don't work. Not now, not ever.

First: Axle wrap is the combination of two motions, not just one as is popularly perceived. The top of the axle will try to rotate forward, as the pinion gear tries to 'climb' the ring gear. Also at the same time, the bottom of the axle will try to rotate backwards. Addressing only one of the motions will leave you will reduced axle wrap, but you will still have it to deal with (broken joints, cracked pinions, seperated shafts, etc)

A 'true' 3 or 4 link, will move in the same arc as the rear axle as it articulates, but will not allow the pinion angle to change. This is traction. A true ladder bar does the same thing. It is welded to the axle, has two attachment points to keep the axle from wrapping both planes.

To understand how a 3 or 4 link works, go to Pirate 4x4 and do a search of the general 4x4 forum, there are threads explaining how it works, and some animated models of it's function. I understand that the needs of a street machine and a rock crawler are very different, but the concepts are still the same, just adapted for your particular application. I could go on for hours on how it works (idea: try 'how stuff works' website, I'll bet something is there too) but won't, I get too excited and start stuttering.