billybix76

Just thought this might be the time for more pinion clarification.....

This was done with driveshaft installed, Adjustable UCA and fixed LCA's and will work on any "one piece" driveshaft including the stocker that came with our 4.0's...yes it's technically a "one piece" as a "two piece" has a center C/V joint or ujoint in addition to the front and rear ujoints....

Using this method you do not even consider measuring any driveshaft angles at all...

1) Jack the car up on stands under the axle tubes with front wheels on ramps or second set of jackstands as close to level as you can reasonably get it.

2) Measure the trans yoke angle realtive to the ground using a magnetic protractor style angle guage. (ie. +2 degrees)

3) Then scoot back and measure the pinion yoke angle. relative to the ground (ie. -5 degrees)

4) Calculate the movement of the font of the pinion nose to get the trans centerline and pinion centerline parallel regardless of the DS angle

5) Turn your adj UCA out, lengthening it, +3 degrees ( in this example) to the positive, nose going up, (by the way you can't do this while the car is in gear or the E brake on, so be careful) so that the rear number is now -2 degree balanced to the front's +2 degree, measured relative to the ground. At this point you have a basic parallel setting from the centerline of the trans shaft and the pinion

The DS position is pointed down from the transmission side and pointed up from the pinion side at this point, just equal, but opposite angles relative to the centerline of the driveshaft, but the trans centerline and pinion centerline will be parallel.

6) double check by measuring the trans yoke angle and then the pinion yoke angle for equal, opposite angles (+ and -) for a net of 0
degrees.

Due to diff gears tending to force the front of the nose of the diff up under power, you shouldn't leave them at parallel and must compensate by now adding in a little more drop in the front of the pinion yoke(or negative angle).

7) Turn the adjustment in, shortening the UCA length, so the diff nose at the pinion yoke drops by -2 dregrees from the new 0 degrees relative position and lock it down...



After driving and settling in, I ended up with about 1.5 negative degrees relative to trans shaft/pinion parallel.

Slacker584

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billybix76

If you lower your car, you may have pinion angle issues using stock control arms......search on "pinion Angle" ...my first post was only an attempt to clear the whole thing up for those who care...If you have a bad pinion angle you will bind the U-joints and possibly the differential pinion bearings and cause vibration/noise and premature wear leading to early failure...If all is stock ignore the post...

Slacker584

Ok thank you. I was just reading that and got a headache trying to understand what you were talking about. I am not the most mechanically inclined person, as you can tell. Looks like a great post though for those who understand the terminology and concepts.