Hot Rods Pinion Angle...Issue or not?

More important than pinion angle is universal joint operating angle. Here is a usful tool to help. If space is limited so u-joint operating angles can't be optimal, than a third u-joint can be added.
Driveline Operating Angle Calculator | Spicer Parts

 

When I set driveline angles, rotate U joints so end caps are parallel from trans and rear pinion yoke. Using ground spacers and magnetic angle indicator. Then compare to drive shaft I set to zero.

As noted earlier, I like +/- 2deg as well. But I also add weight, for driver if suspension is active.

Some cars gain weight over the build processes, I had to change rear coil springs 3x times on one build.

KEY: avoid excess angle, or 0 deg operating angle.

 

This totally goes against any of the hundreds of knowledgeable explanations I have ever seen on this topic. A pinion line parallel to a 4 degree down engine/transmission line would normally be referred to as 4 degrees UP.

-

 

So what direction is the drive shaft going then?

What direction is the flow of power and motion?

Where is the descriptor of direction ( up, down, positive, negative, to the left or to the right) changed, and why? There must be one somewhere an exact point for the three terms , up, down and parallel to be mixed and come fit that drawing.

Super impose ONE simple XY graph over that picture you posted.


Better yet, sit across from someone and tell them how to draw the picture.
So starting on the left draw a line sloped down 2” long, then draw a line 4” long sloped down, then a line 1” long sloped up. See what you get.

 

You see here the shafts are parallel and graphically displayed correctly but some could say the “orientation” of visual representation is confusing because of the protractor mounting.
Some could say the graphic visual shows it’s 92°, some would say 88° some say it’s 2°
The key things here are the shafts ARE PARALLEL and they are also GRAPHICALLY IN THE SAME QUADRANT.
The graph is technically showing 88 degrees.
You need to be smart enough to realize the artist hung the protractor/angle finder on a 90* square. 88° - 90° is negative 2°




This next one is dedicated to MAX effort cars that spend their existence at WOT.
you see how both are displayed the same direction, left to righ, both are negative.



See the use of descriptive language to describe the drive shaft ? Beginning with Left to right orientation,,, you read a direction ( level up down) towards the rear.


Here’s the place where things get screwy.
Obviously the person started with the engine on his left side.
Somewhere along the way the things got turned around. What missing is the frame of reference and the Slop direction.

shown as parallel-
engine down to the rear - pinion down to the rear

Engine down to the rear and pinion up TOWARDS THE FRONT.
The direction change is because the person most likely started with the engine on his left & held the angle finder and walked around to the pinion to the other side of the car and now with the engine on his right and pinion now on his left and called the pinion’s orientation as up.


A set of angles is ALWAYS stated as from going left to right.
Set up some CAD work and draw what you want, say parallel shafts with a sloped drive shaft then measure what you drew.
Play the draw what I say game and see what this brings. Talk to a 5th grader or architect, engineer - “ 3° down sloped drive shaft down and 3°up”

Then try it like this,,, 3° down, sloped drive shaft down - now pick your pencil up move it an inch to the right and down about 1/4”. Restart the line sloped UP back towards the LEFT to be parallel with the first line.

Or perhaps try this- “3° down, sloped drive shaft down, and 3° down parallel with the first line.


Again the correct way to describe this and to draw this is left to right. If you want BOTH the pinion to be parallel with the engine and call it’s orientation as UP because you’ve turned yourself around thus switching the pinion from your left to your right , knowing you’re now describing it in a correct but changed orientation of left to right perspective beginning with the pinion.

You describe it anyway you feel good about it. We can hold to centuries old standards of practice of description, of orientation, except for driveline angles and pinion orientation. Call it up if you want, but at least know it’s up to you because whoever you learned it from instinctually originated left to right but wasn’t smart enough to know they turned themselves and the protractor around.


Things get different when setting up a lowered vehicle. That down first then turn yourself around now it’s up shit don’t work so good.

 

The following is from Spicer Drivetrain Products, a highly reputable driveline company.
The important bit (industry standard procedure?) is highlighted in blue.
Link to site: https://spicerparts.com/anglemaster/measuring-angles

"Step by Step Guide to Measuring Angles
The slope at which a driveline component is installed is a slope of inclination. It is considered either positive or negative depending on whether the slope points up or down when viewed from the transmission toward the rear of the vehicle. A negative driveline slope points down, while a positive driveline slope points up."

The following image from post #65 shows whether the angles are referred to as "up" or "down". The arrows tell the story.....


The angle is always expressed as the lower value (eg: 2 degrees) because it is referenced off a level horizontal plane.
I think you will have a hard time convincing the entire drivetrain industry to change their procedure.

I did managed to get off this bus at the right time, but just had to jump back on........ Why, oh why.....
Little wonder so many are confused about a relatively simple concept.

 

Watch the video .

https://spicerparts.com/videos/measuring-driveline-operating-angles

That picture as many out there are texted wrong.

Spicer said -
When viewed from the transmission towards the rear of the vehicle .

spicer did not say or demonstrate
Except for the pinion , that one you call it towards
the front of the vehicle.

The entire driveline industry doesn’t need their procedure changed.
Just a bunch of brilliant minds that got it wrong, don’t read the whole article, and of course those that get “hoist with their own petard”

 

Notice that it says "points up or down when viewed from the transmission toward the rear of the vehicle".
Also notice that they are talking about the "driveline slope", and not the driveshaft.
Let's use the picture below.


You are in front of the engine and you are looking backwards along the driveline toward the rear of the vehicle.
The transmission output shaft points down (out of the trans towards the rear).
The differential pinion shaft points up (out of the centre section towards the front).
Therefore, in the pic, trans is down 3* and pinion is up 3*.

The video is showing how to calculate universal joint operating angle. While intimately related, it is a different aspect than transmission and pinion angle, and is not described in the same way. Slightly different animals.

...... and, no bang and no smoke. My petard is just fine. I am not hoist as yet.

 

Wow - just wow.
I know you didn’t watch the video, he clearly goes over it,

Everything is towards the rear,
not everything except the pinion,
because the pinion switches and comes back towards the front. Jimenny Christmas. Man study the damn spicer link you posted.
I think you can get it if you actually look at it.
Right now you’re so far behind you think you’re up front.
You’ll probably see that you can’t begin to calculate drive line angles until you get the Up, down thing right.
Watch it twice maybe

 

It is considered either positive or negative depending on whether the slope points up or down when viewed from the transmission toward the rear of the vehicle. A negative driveline slope points down, while a positive driveline slope points up."

That’s says this :
Firstly though ITS VIEWED FROM THE TRANS TOWARD THE REAR OF THE VEHICLE.
Slopes going down are negative and slopes going up are positive,
No fucking where does it say the pinion is up or Down because you switched directions.

Calculate the operating angle of your silly incorrectly texted picture using the method in the video. You’ll be adding when you should be subtracting.
I’m sorry, I’ve been way above your head, I can back up to the beginning and get you up to speed

 

This from the QA1 site ( https://www.qa1.net/tech-center/tech-articles/driveline-angles-pinion-angle-explained )

Measuring Driveline Angles
Using an angle finder that can read within 0.25°, start with the output shaft of the transmission. If the vehicle has the driveshaft installed, rotate the slip yoke so one of the u-joint caps is pointing straight down. Measure the angle of the on the u-joint “ear” where it is machined flat. Take note of the slope and write this down as your first measurement.

Move onto the driveshaft and measure the same way, also taking note of the slope direction. Write this down as your second measurement.

Finally, measure the flat on the rear pinion yoke. Make sure to look at the slope of the driveshaft itself, rather than the direction the output shaft or pinion shaft is “pointing.” The slope is what is important. A transmission output shaft pointing down will have a negative slope, but a pinion shaft pointing down will have a positive slope.

Last paragraph. The red highlighted bit. Surely they are talking about the transmission output shaft pointing down towards the rear, and the pinion shaft pointing down towards the front. Therefore, in the pic we are discussing, the pinion shaft "points" up.

 

Look at this part . Really really good.
Same site, same page just a little further down.


Calculating U-Joint Operating Angle
View the vehicle from from the driver's side (left side). If the slopes are the in the same direction from one member to the next (example: both negative or both positive), simply subtract the smaller value from the bigger value. For example, if the transmission output shaft measures 4° down (negative), and the driveshaft measures 2° down (negative), the calculation would be 4°-2°=2°. If the slopes are opposite (one positive and one negative), add them together.

Did you actually read it ?
If the slopes are opposite ( one positive and one negative), add them together.

So let’s calculate the u joint angles in this setup: that’s what this whole thing is about right?
everything stated from transmission to the rear. The trans and pinion will be parallel.

Trans slope 3* down & drive shaft 2* down
3-2 = 1
First operating angle 1* agreed?

second operating angle.
1 Stated your way,
2 math applied as universally stated by every manufacturer.
Drive shaft down 2* and pinion up 3*
Remember the shafts are parallel,
Math says to add opposite orientation
2+3 = 5 rear joint has operating angle of 5*

Stated correctly according to BOTH MANUFACTURERS DESCRIPTIONS ABOVE
And the trans and pinion are parallel.

driveshaft 2* down & pinion down 3*
Math says subtract same orientation smaller from larger.
3-2=1 Rear ujoint operating angle is 1*

obviously 5* is incorrect and 1* is correct. How’s that? Because in your mix-up of up & Down there’s a deviation from standard practice, standard calculation and a resulting a discrepancy. The deviation is the direction and alternative view of “when viewed from the transmission, down is negative and up is positive and then applying the corespondent math function.
The standards don’t fit with your non standard view, it’s not just you look at all the incorrect pictures, lots of folks will “say” pinion points up and be just as wrong.

Here’s what’s happening Twenty8, I’m trying to teach something and you’re just trying to prove me wrong. Seems we’ve got one thing in common here, we’re both engaged in the impossible.

 

You are absolutely correct in everything you say about calculating the universal joint operating angle, and the negative or positive slope of the components as viewed front to back....... But that is not what I am talking about here, and not where this discussion startred it's journey. It started regarding the up and down terms that are often used to describe transmission output shaft and pinion angles.

The terminology used for a downward pointing transmission shaft has always been "x degrees down" (or pointing down). A pinion shaft on the same slope (ie: parallel to the slope of the trans shaft) has always been described as " x degrees up" (or pointing up). That is just the way it is. I am not making any judgement as to whether it flies or not. Just going by the commonly used and accepted way it is described. Again, this is NOT describing anything to do with u-joint operating angle.

Anyway, enough fun. My sides hurt, and it is getting dangerously close to becoming a slanging match, and I won't be drawn into that. I hope a driveline guru can chime in and referees us as to one train of thought or the other..........

On a more humorous note, it appears that we have rated a mention in the "Pet Peeves" thread...

 

You still haven’t watched the video yet have you?
The spicer video , you brought the spicer link too I posted the video-
where he physically measures and calls Down for pinion.
Moves to dry erase board and
Then he draws a parallel line to trans. He’s previously called the transmission down and on a negative slope.
Then the part where he then correctly subtracts both negative angles because they are both negative.
Both slope downward to the rear

Since down slopes are negative, and upslopes are positive and all readings are viewed from trans to rear of vehicle,,,, pretty sure we all got that proven,,,, why oh why does the pinion get called opposite?

Please pick the exact location in the chain of every parameter, every descriptive statement, and every proper function of math gets special treatment equivalent to “opposite day” for the pinion.

 

Yes, I have watched the video. And also yes, it is really handy to be able to understand the two differing terminologies used to describe the orientation of the trans and pinion. We can go on ad infinitum about what is the "correct" method of description, but the fact is that people do, and always will, use one or the other. Both ways work fine, as long as you are aware of the method being used and are on the same page.

Let me see if this puts your mind at rest as to whether or not I grasp it.
Trans shaft sloping down towards the rear = negative slope/angle = some say the transmission is "tail down".
Pinion shaft sloping down towards the rear = negative slope/angle = some say the pinion is "nose up".
Pinion shaft sloping up towards the rear = positive slope/angle = some say the pinion is "nose down".

Again, not interested in correct or incorrect terms. If both sides of the coin are understood, it really doesn't matter....

Do I scrape through with a pass???
I have read a lot of your stuff in the past and I am not at the level you seem to be at, but I am comfortable with this stuff.

 

@twenty8 I’ve heard nose up/down before, but why if the pinion is pointing up, it would be considered nose down and vice-versa?

 

Because terms are descriptive, terms define operations, terms are used to determine specific locations and in a written form of communication that’s all you got.

Say you were spotting hits for a guy zeroing in a rifle scope. You are spotting and hes shooting. You’re supposed to tell him where he hit and with universally descriptive terms you tell him exactly where he hit. His job is to adjust the scope. Just imagine what happens if in your mind it doesn’t matter and you started telling him what to do with the scope instead of what he hit. He shoot’s high and left and that’s what he needs to know. () But since sticking to pre set parameters and understanding of universal practices or terms doesn’t matter )) he’s hit high left, but you tell him down and right because that’s what you want to do with the scope. He will adjust the scope up, and adjust left. Next shot is way left and way right. Perhaps if you told him hey you need to move the scope like I’m telling you instead of me telling you what you hit,,, but the pre set parameters are no longer adhered to.
Without parameters and terms he hits nothing unless he sees it, so if he sees it he don’t need you confusing or confirming.

You want to use “nose orientation” and deviate from the main parameter?

There’s obviously universally understood way to actually do this correctly. The parameters and terms and math are clearly laid out. Follow them correctly till the end and things get sorted correctly.
Switching the parameters at some arbitrary point near the pinion leads to the confusion, it’s a direct path to all the confusion around such a simple thing as pinion angles. The “opposite switch” is the key that unlocks the door of confusion.

The bottom line is achieving a correct operating u joint angle. That’s the final step. But in order to reach that all the information above or infront of it must be correct and uniform. If it cannot be uniform from human intelligence inability then the exact place where the switch from the pre set parameters switches should be noted so that everyone can be aware and follow the rule switch.

A single picture is worth 1000 words, the problem is there’s couple hundred pictures that include wrong text,


I know we’re in a crazy world today, but wouldn’t it be great if people who needed to set up their first drive line could easily understand how. It’s either follow the parameters to the very end or follow the parameters set forth until this very point and then you switch them to opposite.

 

It can’t be that way, hence the mystery and confusion around pinion angles.


The first rule is “everything viewed from the transmission to the rear”. ((( does the term everything still mean everything or has it changed too)))

The second rule is “ down slope (rule 1) are negative and up slope ( rule 1) are positive. ((( up and Down hasn’t been changed)))

The third rule is math “ when the slopes are both (rule 1&2) negative - subtract the smaller from the larger, when both slopes are both (rule 1&2) positive you subtract the larger from the smaller , if slopes are opposite meaning one (rule 1&2) positive and one (rule 1&2) negative then you must add. ((( negative and positive still the same meaning,, clearly defined in rule 1&2)))

There’s 3 simple rules, only 3 and each based on the one prior.
Don’t make anything like an unspoken 4th rule and you’ll be fine. Don’t switch meanings or exclude anything from the term “everything” and you’ll be fine. Don’t deviate from rule 1 in any way.
Perfect every single time, pretty simple and easy.

Especially don’t add a fourth rule that violates any parameter set forth in rule 1, 2, 3.
That sabotaging imposter 4th rule would include a violation of rule 1 and thus changing directions. The imposter sabotaging 4th rule would require that you violate rule 2 and call that negative slope on the pinion as up. The imposter sabotaging 4th rule would require you to violate rule 3 exactly correctly (((( can one violate any rule exactly correctly))) and and fuck everything up or seek help and run into nothing but confusion about people explaining why or which parts of sabotaging imposter rule 4 is more important.

 

It gets confusing, doesn't it? That is what I have been trying to say all along. People use different terms for the same thing and if you are not aware of what they mean the calculations can be incorrect. I will try to explain as simply as possible (and 31Vicky with a hemi will let me know if I get it wrong).

Let's use the following diagram. I only chose it because it clearly shows the slopes of the components. Ignore the numbers.

The proper way to describe the slopes is going from the front to the rear (trans to the differential).
In the diagram, you would say:
Transmission output shaft slopes down (negative slope)
Coupling shaft (1st shaft) slopes down (negative slope)
Driveshaft (2nd shaft) slopes down (negative slope)
Pinion shaft slopes down (negative slope)
As you can see in the diagram, all the components are sloping down when viewed from the front towards the rear.
Sometimes components can slope the other way (upwards towards the rear). It would then be called a positive slope for that component.

Now, we will move on to the bit that catches a lot of people out.

Some people will use the terms "tail up" or "tail down" to describe the transmission angle. Just as it sounds, the tail is the rear of the transmission. This doesn't usually cause problems because it works the same way as the slope. If the transmission was said to be "tail down", it would be like the diagram shows, so the slope is down. Hard to get mixed up as both descriptions say "down".

The differential is sometimes described as "nose up" or "nose down". The word "nose" is used to describe the actual pinion flange on the front side of the centre section. This is where we need to be very careful.
The diff in the diagram above would be "nose up", but using the proper terminology it slopes down towards the rear (negative slope). The two different ways used to describe the pinion conflict. "Nose up" = "slopes down".

So you can see that it is very important to understand which method is being used to describe the pinion.
Using slope (from front to rear) is the proper way, but some people will always still use the nose term.
That is what I have been saying throughout this debate. It is more important to be aware of both of the ways used to talk about pinion angle than to argue which one is "correct". If you can identify exactly what is being described, your calculations will work.......... My pinion angle rule number 1: Know the exact term being used !!! .....

@Budget36 , let me know if this makes sense to you. I hope it does.
The next step would be to then calculate the universal joint operating angles.
If you have read all the way to here you have done well. A lot of people will simply not bother to read long posts, so very little changes in the "collective understanding".

 

Wow, pinion angle posts never disappoint. We were overdue. @31Vicky with a hemi has always had a clear understanding of the function and purpose, one needs only to do a search and see the answer is always the same. The confusion always derives from "angle to what" as if all measures are from dead level to the ground. Oops. Any swing of the axle moves this shit where it has to go. I'm with vic, on ladder bars pinion angle doesn't change. The relationship to all the parts the axle works with, i.e. the trans, driveshaft, the universals, they do. Does it change from static at rest? Well WTF, yeah. It has to unless you have no suspension. Let's argue about that instead of getting the message.

But, what if the OP's axle was fabbed with a TIG welder. Did that super high voltage create a tear in the wormhole we exist in. Now I'm scared...

 

I’ll just refer you here.
https://www.jalopyjournal.com/forum/threads/pinion-angle-there’s-no-4th-rule.1301685/
the first half of your above post was great.

“Now we move to bit that catches people out”
From there you’re entering that 4th rule and use too many words to describe why the first parts are to be violated.
Only the 4th rule is confusing
https://www.jalopyjournal.com/forum/threads/pinion-angle-there’s-no-4th-rule.1301685/

 

@twenty8 Your first sentence has summed it up for me.
I’m in the process of staying within the rules, but playing a different game.
In my ‘32 Dodge PU I set the transmission down 3, pinion up 3, but the driveshaft is only going to be about 18 inches long.
I think my Google geometry showed I’d have like 9 or 10 degree operating angles. I’m not comfortable with that. So time to make some adjustments

 

Well, thank you.......... I think.
I agree that following what you call rules 1, 2 & 3 is the way to go. We are on the same page there.
Just to be clear about what you have decided we should refer to as "the 4th rule". I have not been advocating the use of nose up and nose down when talking about the pinion. The fact is that those terms are used by some, and that can be why many people get mixed up about this subject. Surely it would be less confusing if people were aware of exactly what to look out for. That is all I have been trying to do, make people aware.
I think maybe we are chewing on the same bone, but at different ends.......

 

I hope you don't mind if we use you as an example here so we can help others to understand.
So, let's run through it and make sure of what you have.

Transmission down 3*: The transmission output shaft is sloping down 3* towards the rear, correct?

You say Pinion up 3*: This is what needs to be clarified. Is your diff the same as in the diagram below, or is it opposite (eg: sloping up towards the rear)?

To then calculate the uni joint operating angles we will also need to have the driveshaft slope/angle.

 

Yes, same as the pic you show, but with a single driveshaft.
Let me take an extreme example.
Two equal but opposite slopes at 100 feet apart. The slope between those two are minimal (ie say one begins the slope 4 inches higher/lower than the other). Now shorten the distance to 6 inches, the slope is more severe.
Not being a person who has been there done that many times, I went 3 down, 3 up. Then the “oh my” set in when I put the transmission and cross member in.
So I’ll be changing engine/transmission angles and pinion angles to keep a proper operating angle for the Ujoints.
Can’t be any different than driving up or down a hill as far as the drivetrain is concerned

 

“ The fact is that those terms are used by some, and that can be why many people get mixed up about this subject. “
Yes it’s a clear an obvious fact.
It only happens because people want to dabble around with rule 4.
No switchie guarantee no confusie

 

Ok, let's use the proper way to describe what you have. Let's talk using slopes as viewed from front to rear.
Your transmission slopes down 3 degrees towards the rear (like the diagram).
Your pinion shaft slopes down 3 degrees towards the rear (like the diagram).

We will still need to know what slope/angle the driveshaft will be to go any further.
1). Will the driveshaft slope up towards the rear or down towards the rear?
2). Can you run a straight-edge from the tip of the transmission shaft to the centre of the pinion flange and get an angle?
If not......
3). Sitting at ride height on a level surface, can you get the following measurements?
***Height of the trans output shaft tip from the floor (vertical).
***Height of pinion flange centre from the floor (vertical)
***Distance between the tip of trans output shaft and the centre of the pinion flange (measured level horizontally). These two points can be transferred accurately to the floor and then measured.

Shorter driveshafts do need more attention as the angles can get quite severe.

 

^^^clearly found somewhere in rule 4 ^^^

There no clarity or clarification needed. Unless of course you’re into the imposter rule #4. Rules 1,2,3 have everything, clarified, clearly and precisely before beginning.

 

Read Budget36's reply in post #85. It shows that he is mixing up the terms.
Would you like to help him out or not? Who knows, maybe we can save some other souls along the way....

 

@Budget36 , you can PM me about this if you want.
I would prefer to keep it here out in the open so any bad information can be pointed out, and also so others can follow along and get a better handle on this. Your choice.