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Theres a couple post recently about pinion angle and or a rear end. I didn't want to hijack their threads so I'll post my own. When removing the whole rear axle housing, should you measure the pinion angle FIRST, so you can put it back the same degree? No matter what rear you have. Is there a spec? Couldnt find one. Thanks

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5 to 7 degrees, NOSE DOWN according to the Mopar Performance Chassis Book. This angle is called the drive pinion angle. Drive pinion angle is the
angle between the driveshaft centerline and the centerline of the axle (rear end) drive pinion. This spec is for BOTH stick and
auto setups!!

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Pinion angle is the relationship between the transmission centerline and the pinion centerline, not to the driveshaft and not to the ground.

Ideally, the pinion should become relatively parallel to the transmission as the pinion wraps up under power.
This is how U-joints are designed to run.

Make the pinion parallel to the transmission as a base line, then tip the pinion downward 2 degrees (for a street car). This is referred to as 2 degree negative pinion angle.

As a rule of thumb, I don't like to run more than a true 4 degree negative pinion angle.

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Pinion angle is the relationship between the transmission centerline and the pinion centerline, not to the driveshaft and not to the ground.

Ideally, the pinion should become relatively parallel to the transmission as the pinion wraps up under power.
This is how U-joints are designed to run.

Make the pinion parallel to the transmission as a base line, then tip the pinion downward 2 degrees (for a street car). This is referred to as 2 degree negative pinion angle.

As a rule of thumb, I don't like to run more than a true 4 degree negative pinion angle.

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Doctor Diff, i think that we ARE on the same page with the pinion angle. Mopar refers to negative
pinion angle AS nose down! The centerline of the
driveshaft IS extended as a straight line through
the transmission output shaft. The ground is NEVER
used! Not arguing with you, but just simply reinstating what is in the manual. The 5 - 7 degree angle is correct with the lowest setting
used according to the "bite" or "hook". There is
no indication of these settings being different for superstock or XHD springs. 4 degrees will work
if the car hooks at that setting for you. 5-7, however is the baseline and you can work up or down from those settings.

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The centerline of the
driveshaft IS extended as a straight line through
the transmission output shaft.

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The centerline of the
driveshaft IS extended as a straight line through
the transmission output shaft.

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I suppose there is only one remote instance where you can simply measure the shaft to pinion angle and come up with a proper pinion angle measurement. When the driveshaft centerline is dead nuts in-line with the crank/tranny centerline.

The proper way is to take the shaft completely out of the equation and just check crank centerline to pinion centerline.

The idea of course is to predict the proper axle wrap up under load so that DrDiff said, the crank and pinion are parallel. This ensures both sets of u-joints are operating at equal angles and canceling each other out under power.

There is simply no way to check just the driveshaft to pinion angle and come up with that figure.

I also have never understood how you can adjust pinion angle to adjust hook. The only way I can see is that with improper pinion angle will create a bind that can hurt hook.

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Mopars, being blessed with the excellent suspension they have, are the easiest to tune for
traction. The rear end goes through a balance of
two major forces acted on it. Left to right (torque twist to counteract the natural motion of
of the driveshaft motion of right to left) and the upward motion of the pinion (counteracting the downward force of the ring gear being turned).
As the pinion rises up to the body under torque on
the ring gear, the front half of the springs bends
to compensate the pinion rising above the transmission centerline (imagine a straight line from the rear of the trans to the pinion). This rise is positive (angle). Not good!! Causes wheelhop and hurts the suspension. Now the engineers figure out a way to combat this problem,
by PRELOADING or setting negative (nose down angle) below the trans - pinion centerline. Once the car is accelerating, this angle becomes straight and the pinion is in plane with the transmission. Thus the rear end is receiving 95-to nearly 100% torque from the motor/trans save for parisitic losses. And the springs are not as bent to create wheelhop and jounce. The pinion snubber aids also by taking the upward force of the pinion and raising the body upward and slightly rearward to HELP weight transfer to the rear wheels. All this gives better launches/60ft
times and a stable suspension while under acceleration. The rear end rotation from left to right is a reverse reaction to the torque placed on the ring gear. Superstock springs compensate for this by having more spring halves on the front half of the right spring than on the left.
The rear is level and you have maximum traction or
"bite or hook". The car leaves straight and nearly
level, depending on chassis age, level of tune in
motor/drivetrain and TOTAL WEIGHT (w/driver). All
these factors considered will make for a well-balanced ride.

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I also have never understood how you can adjust pinion angle to adjust hook. The only way I can see is that with improper pinion angle will create a bind that can hurt hook.

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Mopars, being blessed with the excellent suspension they have, are the easiest to tune for
traction. The rear end goes through a balance of
two major forces acted on it. Left to right (torque twist to counteract the natural motion of
of the driveshaft motion of right to left) and the upward motion of the pinion (counteracting the downward force of the ring gear being turned).
As the pinion rises up to the body under torque on
the ring gear, the front half of the springs bends
to compensate the pinion rising above the transmission centerline (imagine a straight line from the rear of the trans to the pinion). This rise is positive (angle). Not good!! Causes wheelhop and hurts the suspension. Now the engineers figure out a way to combat this problem,
by PRELOADING or setting negative (nose down angle) below the trans - pinion centerline. Once the car is accelerating, this angle becomes straight and the pinion is in plane with the transmission. Thus the rear end is receiving 95-to nearly 100% torque from the motor/trans save for parisitic losses. And the springs are not as bent to create wheelhop and jounce. The pinion snubber aids also by taking the upward force of the pinion and raising the body upward and slightly rearward to HELP weight transfer to the rear wheels. All this gives better launches/60ft
times and a stable suspension while under acceleration. The rear end rotation from left to right is a reverse reaction to the torque placed on the ring gear. Superstock springs compensate for this by having more spring halves on the front half of the right spring than on the left.
The rear is level and you have maximum traction or
"bite or hook". The car leaves straight and nearly
level, depending on chassis age, level of tune in
motor/drivetrain and TOTAL WEIGHT (w/driver). All
these factors considered will make for a well-balanced ride.

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Some very good info here. My question is how is the best way to check the transmission angle, in relation to the pinion angle. Do you measure off the yokes?
Second, I have a 67 B body that I have had a very long time. Over the coarse of years it has had a 440, a 426 Hemi, different torque converters,drive shafts, a Dana and a 8 3/4 rear. It has had different wheels and tires and different sets of gears.
The one thing that has always stayed is the surging vibration. If you run the car hard up to 80 mph and up you can not see out of the mirrors and everything in the car is shaking and vibrating. Sometimes very violent, and the next time hardly at all.
One night on the interstate the back of the transmission went south at about 130 mph . After all of these changes could this all be caused by the pinion angle? The only thing that I don't believe has been changed is the rear leaf springs.

Thanks
Dan

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Did you use the XHD spring and never changed them out after so many years? Or did you use the factory 440 Magnum hd spring with the same duration of use? Weak springs GIVE a LOT of positive pinion angle (nose UP) when worn!! Note: HEMIS (all trans) and 440-6pack (all trans)440 Magnum (4speed ONLY w/DANA) use the SAME XHD spring. ALL 340, 360 HP, 383-400-440 Magnum engines (440's w/auto and 8-3/4 or DANA rears) use the "standard" HD spring.