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I have a 71 Hemi Cuda clone with Alter K and Tremic 600 5 speed trans and 8 3/4 (for now) rear that I am setting up. I have 4 * down in the tailshaft of the trans, 1* down towards the rear on the driveshaft and 0* pinion.
Are these acceptable angles? I thought the pinion should point down.
Also, what's your thoughts on pinion snubber, get an adjustable or keep stock? Car will be 99% street, but driven.

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In your example even though it is not completely out of an acceptable range according to the article, I would set your pinion at 2* up so that under power it would be at 4* up cancelling out the 4* down you have at the output shaft.

It I am dead wrong someone will correct me.

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One thing the article doesn't point out is that your pinion angle should be 2* less than what you need to zero out. The reason for this is that undo torque (driving conditions) your pinion will rotate up roughly 2*, more under hard accel, less in coast or braking, but constant drive torque is 2*. So if your trans is down 3* you need pinion up 3* in driving conditions to cancel out the angle. In this example I would set my pinion at 1* up knowing that under driving conditions it will twist up 2* for the total of 3* needed for minimum vibration.

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The big thing to keep in mind on pinion angle and driveshaft angle is at the rear U joint the pinion shft and driveshaft should never be perfectly aligned sitting still, there should be visible V, even if it is only 2 to 3 degrees difference Never a upside down V All U joints need a difference in angle for them to work correctly, the needles need to rotate due to the diffeence in rotating angles or planes

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On a big tire/chassis car many times the centerline of the crank is lower than the centerline of the pinion. This makes the driveshaft run "uphill" towards the rear axle, leaving the rear u-joint angle in an "upside down V".

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The big thing to keep in mind on pinion angle and driveshaft angle is at the rear U joint the pinion shft and driveshaft should never be perfectly aligned sitting still, there should be visible V, even if it is only 2 to 3 degrees difference Never a upside down V All U joints need a difference in angle for them to work correctly, the needles need to rotate due to the diffeence in rotating angles or planes

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On a big tire/chassis car many times the centerline of the crank is lower than the centerline of the pinion. This makes the driveshaft run "uphill" towards the rear axle, leaving the rear u-joint angle in an "upside down V".

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I can't imagine a car with the pinion yoke at a lesser angle , even on a four link car with big tires and a low crankshaft centerline like your describing, having the pinion yoke at a lesser angle, A upside V pointing so it(the pinion yoke) will go up under acceleration increasing the misalignment I have ran ladder bar cars that where set up that way when I got them I ended up changing it so there was 1 to 3 degrees in the proper V, that didn't really seem to make much difference but that was on a car built in New York state that had single adjsutable 3 inch travel rear shocks on it It was foot brake car that would top the rear shock travel out when stalling the motor all the way up against the converter so ther was no suspension travel left Lots of different ways to get results, not all results are the same or the best

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The big thing to keep in mind on pinion angle and driveshaft angle is at the rear U joint the pinion shft and driveshaft should never be perfectly aligned sitting still, there should be visible V, even if it is only 2 to 3 degrees difference Never a upside down V All U joints need a difference in angle for them to work correctly, the needles need to rotate due to the diffeence in rotating angles or planes

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On a big tire/chassis car many times the centerline of the crank is lower than the centerline of the pinion. This makes the driveshaft run "uphill" towards the rear axle, leaving the rear u-joint angle in an "upside down V".

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I can't imagine a car with the pinion yoke at a lesser angle , even on a four link car with big tires and a low crankshaft centerline like your describing, having the pinion yoke at a lesser angle, A upside V pointing so it(the pinion yoke) will go up under acceleration increasing the misalignment I have ran ladder bar cars that where set up that way when I got them I ended up changing it so there was 1 to 3 degrees in the proper V, that didn't really seem to make much difference but that was on a car built in New York state that had single adjsutable 3 inch travel rear shocks on it It was foot brake car that would top the rear shock travel out when stalling the motor all the way up against the converter so ther was no suspension travel left Lots of different ways to get results, not all results are the same or the best

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The scenario I'm describing is similar to the middle one in the chart, and where it is a big tire chassis car. The engine/trans is 2* down which ends up putting the centerline under the pinion. I don't agree with the 2-3* correction on a ladder bar car - adding 1-2* is plenty unless your bars are junk. Puts the engine at 2* down, the driveshaft runs slightly uphill, and the pinion at +0-1*, leaving the (slightly) upside down V.

In MOST cases Under power) the ^ is in the front and the v is at the rear. There are situations where it is reversed, as I described. From a vibration standpoint, it doesn't matter at which end they are as long as there is one of each to cancel the angles out. Pretty simple concept to grasp.



Also, closed minds seem to automatically try to manipulate the pinion angle by changing the rear axle, when sometimes it is actually the engine at the wrong angle, and that should be changed, not the axle.

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Thanks for all the input guys. So what I am hearing is that as long as the engine/trans angle is opposite of the pinion angle, I am good and dont concern myself what the driveshaft is doing, correct?
So in my scenario with a street driven vehehicle with 700 HP, on a level floor, the trans is down 4* so the pinion should be up 2* allowing for a few more degrees further up rotation while under load?
Thanks!

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That's the way I see it.

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Thanks for all the input guys. So what I am hearing is that as long as the engine/trans angle is opposite of the pinion angle, I am good and dont concern myself what the driveshaft is doing, correct?
So in my scenario with a street driven vehehicle with 700 HP, on a level floor, the trans is down 4* so the pinion should be up 2* allowing for a few more degrees further up rotation while under load?
Thanks!

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Part of the confusion of pinion angle settings is that you are trying to take an educated guess at how much the pinion angle will change under load. The generally accepted change for leaf spring cars is 3-5* for auto cars and 5-7* for sticks. Obviously a high H/P car with soft springs will wrap the springs up more than a low H/P car with stiff springs, and a car with clamped front segments and/or slapper bars, Cal Tracs, etc may be only 1-2* deflection. And here's the rub - there's also u-joint operating angle to consider. And while on paper your car, with the trans pointing down 4*, you should need the pinion at 0*, so your leafs can let the pinion rotate 4* up to make the math for pinion angle work - that may leave your u-joints with no operating angle, (the engine/trans/driveshaft/pinion are all in line)and prone to fail from brinelling. That's why I mentioned that sometimes you have to change the engine centerline to correct the pinion angle. I'm sure there will be some that disagree, and this subject has been beat to death in the race forum. It may take several adjustments to get the whole package where you want it.

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Mr. Spirit,

A question for you so that I might learn no argue, are you saying on a street driven normal use street car you would set the pinion to allow for 4-5* wrap up on an auto and 5-7* on a stick? In the end at cruise speed I would think that the maintained torque/wrap would be the same for either one. Now in a holeshot/hard accel situation I could see the violent action of a stick wrapping up more and I could see a quarter mile car under constant accel until it's shut down sustaining a 4-5* wrap up. My specs were told to me long ago and I have set up many at 2* with no ill effects and to my knowledge never had to go back and adjust due to a vibration.

Thanks for your input.

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Part of the confusion of pinion angle settings is that you are trying to take an educated guess at how much the pinion angle will change under load. The generally accepted change for leaf spring cars is 3-5* for auto cars and 5-7* for sticks. Obviously a high H/P car with soft springs will wrap the springs up more than a low H/P car with stiff springs, and a car with clamped front segments and/or slapper bars, Cal Tracs, etc may be only 1-2* deflection. And here's the rub - there's also u-joint operating angle to consider. And while on paper your car, with the trans pointing down 4*, you should need the pinion at 0*, so your leafs can let the pinion rotate 4* up to make the math for pinion angle work - that may leave your u-joints with no operating angle, (the engine/trans/driveshaft/pinion are all in line)and prone to fail from brinelling. That's why I mentioned that sometimes you have to change the engine centerline to correct the pinion angle. I'm sure there will be some that disagree, and this subject has been beat to death in the race forum. It may take several adjustments to get the whole package where you want it.

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Mr. Spirit,

A question for you so that I might learn no argue, are you saying on a street driven normal use street car you would set the pinion to allow for 4-5* wrap up on an auto and 5-7* on a stick? In the end at cruise speed I would think that the maintained torque/wrap would be the same for either one. Now in a holeshot/hard accel situation I could see the violent action of a stick wrapping up more and I could see a quarter mile car under constant accel until it's shut down sustaining a 4-5* wrap up. My specs were told to me long ago and I have set up many at 2* with no ill effects and to my knowledge never had to go back and adjust due to a vibration.

Thanks for your input.

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Your driveline could very well be "happy" with only 2* pinion angle, if the front spring segments don't deflect much under power, whether it's from a lack of traction or a from having a stiff spring package. But you can have a car that drives beautiful on the street with street tires perform horribly at the track with slicks, developing a vibration from excessive spring deflection ruining the pinion/u-joint angles. Leaf spring cars usually need some help to keep the angles in a happy zone, to keep the angle from changing much from cruise to high traction launches. Clamping the front spring segment, slapper or Cal Trac bars, etc. are ways to limit the change in pinion angle under power that doesn't happen with ladder bar or 4 link cars, not to mention the angle changes that happen as the car changes ride height under launch.

Keep in mind that leaf springs are a poor choice for rear suspension - a spring, by nature, is supposed to absorb, store and release energy - not what you want to transmit energy from the rear axle to the car, due to the spring trying to wrap up and flatten back out. They can be made to work very well with "crutches" to reduce their inherent problems - many times with a lot of trial and ERROR. Just be aware that with leaf springs the pinion and u-joint angles are at the mercy of how well you can match spring function to traction.

Again - this subject has been beat to death in the race forums, with many opinions on how to measure it or the optimum setting. The end result is the optimum setting that u-joints can live under without creating vibration varies greatly from car to car. What generally works is that while under power a slight u-joint angle and the engine/trans/pinion centerlines are aligned. How to achieve that is the fun part.

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Thanks for all the input guys. So what I am hearing is that as long as the engine/trans angle is opposite of the pinion angle, I am good and dont concern myself what the driveshaft is doing, correct?
So in my scenario with a street driven vehehicle with 700 HP, on a level floor, the trans is down 4* so the pinion should be up 2* allowing for a few more degrees further up rotation while under load?
Thanks!

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You have a PM Never have the pinion angle pointed up away from the driveline in any stock type leaf spring suspension, never I have a 8 3/4 pinion shaft that is in two pieces from a 4x4 that a "real mechanic" from a junkyard installed the spring perches on so the pinion angle was higher than the driveline angle,it broke in half the second time the owner jump on it All leaf spring type rear susensions, unless they are using a floater or slider mount on ladder bars or four link will pitch the pinion up under acceleration, not good If everything is aligned perfectly straight like in non suspension race cars you don't need U joints, only a solid connector from the trans to the pinion yoke On our type of cars with U joints you need to have a difference in angle on all the joints in the driveline when running down the road at part throttle and at WOT as well as when coasting under no power so the needles have to rotate in the cups. No magic, the hard part is getting everything aligned properly when parts change alignment under power and when not under power The u joints don't know the difference in angles from left to right and from up and down, the rear U joint and tranny yokes will know when overly misaligned Most of my lessons are hard learned from drag racing Mopars, not from reading books and studing theory This rear u joint was broken at the track in my old pump gas duster with a 727 in it on M/T ET Street tires, not slicks I have a tranny yoke from the same car that I was going to put besides this U joint Of course I can't find it now It has half the yoke missing, the part the U joint presses into broke and stayed on the U joint in the driveshaft Driveline parts will break when misalgned and over stressed I would never have a upside down V angle (The pinion pointed up and the drivesahft pointed down) between the pinion angle and driveshaft angles when sitting still, NEVER

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There is so much misinformation on driveline angles, pinion angles and trans and pinion angles compared to each other it is absolutely sickening

you are correct on wanting your pinion angle more down when sitting still, never, never run it pointed up towards the tranny

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The u joints don't know the difference in angles from left to right and from up and down, the rear U joint and tranny yokes will know when overly misaligned

stressed I would never have a upside down V angle (The pinion pointed up and the drivesahft pointed down) between the pinion angle and driveshaft angles when sitting still, NEVER

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The u joints don't know the difference in angles from left to right and from up and down, the rear U joint and tranny yokes will know when overly misaligned

stressed I would never have a upside down V angle (The pinion pointed up and the drivesahft pointed down) between the pinion angle and driveshaft angles when sitting still, NEVER

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Since you are correct in stating the u-joint doesn't know left/right/up/down - here's a sloppy chart to show some scenarios. All are viewed from side and referenced to ground.

Top one is engine level, u-joint 4*^,(driveshaft 4* dn) u-joint 4*v, pinion level.
Next is engine 2* dn, u-joints 2*^,(driveshaft 4*dn) u-joint 2*v, pinion 2*up.
Next is engine level, u-joints 2*v, (driveshaft 4* up) u-joint 2*^, pinion level.
Bottom is engine 2* dn, u-joints 4*v, (driveshaft 4* up) u-joint 4*^, pinion 2*up.

All scenarios leave the engine/trans and the pinion centerline parallel . Top 2 are typical street car - bottom 2 are more chassis/big tire oriented.

And again - these are UNDER LOAD scenarios - how much more the pinion needs to start out pointed down from these figures vary by suspension type - could be anywhere from 1-7*.

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Why would anyone, epscially a drag or road racer want to set thier rear ends up like the bottom two are I would lower the pinion angle down so it had at least two or more degrees difference(than the drivshaft angles) at static and maybe move it down more after trying that, more is better sometimes to start with, epsecailly on leaf spring cars The pinion shaft will always try rotate up under acceleraton, correct

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The u joints don't know the difference in angles from left to right and from up and down, the rear U joint and tranny yokes will know when overly misaligned

stressed I would never have a upside down V angle (The pinion pointed up and the drivesahft pointed down) between the pinion angle and driveshaft angles when sitting still, NEVER

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Since you are correct in stating the u-joint doesn't know left/right/up/down - here's a sloppy chart to show some scenarios. All are viewed from side and referenced to ground.

Top one is engine level, u-joint 4*^,(driveshaft 4* dn) u-joint 4*v, pinion level.
Next is engine 2* dn, u-joints 2*^,(driveshaft 4*dn) u-joint 2*v, pinion 2*up.
Next is engine level, u-joints 2*v, (driveshaft 4* up) u-joint 2*^, pinion level.
Bottom is engine 2* dn, u-joints 4*v, (driveshaft 4* up) u-joint 4*^, pinion 2*up.

All scenarios leave the engine/trans and the pinion centerline parallel . Top 2 are typical street car - bottom 2 are more chassis/big tire oriented.

And again - these are UNDER LOAD scenarios - how much more the pinion needs to start out pointed down from these figures vary by suspension type - could be anywhere from 1-7*.

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Why would anyone, epscially a drag or road racer want to set thier rear ends up like the bottom two are I would lower the pinion angle down so it had at least two or more degrees difference(than the drivshaft angles) at static and maybe move it down more after trying that, more is better sometimes to start with, epsecailly on leaf spring cars The pinion shaft will always try rotate up under acceleraton, correct

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Why would anyone, epscially a drag or road racer want to set thier rear ends up like the bottom two are These are dictated by the engine/trans installed height and the diameter of the tires - so would YOU raise the engine, or put smaller tires on to "correct" this? I would lower the pinion angle down so it had at least two or more degrees difference(than the drivshaft angles) at static and maybe move it down more after trying that, more is better sometimes to start with, epsecailly on leaf spring cars. READ where I said the figures were (Big words, sound them out) UNDER LOAD, and 1-7* additional pinion angle would be needed, according to suspension. Not to mention that the two lower examples would likely be big tire chassis cars that wouldn't likely have leaf springs.

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Pinion angle is easy to understand once you realize the pinion should become PARALLEL to the transmission when the vehicle is under power.

This is true regardless if the rearend is mounted higher or lower than the engine.

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Obviously much easier for some of us to realize than others.