Hot Rods Pinion Angle...Issue or not?

You can still have a vibration or eat up U joints if things aren't set up right with truck arms.
The real thing/concern here is vibration and premature U joint wear or failure.
Every time this pinion angle thing comes up I remember the Ricky Racers of the 60's and 70's who argued that you had to have the pinion angled down at X degrees to compensate for spring wrap on launch at the drag strip. I can remember some of the local guys going to great lengths say why you did that but they were the same guys who were always breaking the rear U joint and puking the driveshaft on the line at the strip or a few times in the middle of street while showing off.

Very simply it is going to vibrate a bit because at some point in drive shaft rotation the joints want to bind up a bit but if they don't bind up, no vibration, It can wear U joints prematurely if the angles are off but That might depend on how far and how much you drive the car. Squirrel puts more miles on his Nova during drag week than 50 % of the guys on here put on their "street driven" rods or customs in a year. Simply meaning that Wearing out a U joint in 20 K rather than 70 K might not be a real issue time wise as it may take several years to rack up that 20K.

On that car I am not seeing a lot of room to raise the rear of the trans or make changes anyhow. Engine angle through the crankshaft and main/outout shaft usually depend more on keeping the carb sitting level than anything else. If the carb is sitting level you work around it best you can. If it costs a little extra U joint wear that might be worth it in the end.

 

When the engine/trans are 4 degrees down, I have always mounted the pinion 4 degrees up. Without actually seeing your setup, I'd be inclined (pun intended ) to say your angles are off by quite a bit. However, if you were to adjust your pinion angle, from the looks of your pic, you could end up with clearance issues with your floor, especially if you intend to loosen up the rear suspension.

Again, not seeing things in person here ... if you aren't feeling any vibration etc, well .....

 

When describing a set of angles either verbally or graphically , in any scenario including driveline angles it’s always left to right and orientation remains the same.
Engine trans + drive shaft+ pinion the orientation and frame of reference is always the same..
Your engine is 4° down then you want the pinion parallel and also verbally as 4° down.
Unless of course you want a set of intersecting angles that are not parallel, then by all means set it at 4° Up.
or if you’re actually meaning you turned yourself and angle finder around and now the frame of reference is different or opposite and left now right and right is now left and not sure what makes a difference or not.

 

One of the more common images of Pinion angle and parallel shafts.

 

The pinion angle is not referenced to the ground, but to "level". Usually the vehicle is placed on somewhat level ground when doing measurements, but the ground isn't the reference point.

The ground is used as a reference point for setting up the ride height .

So what is being measured when comparing the relationship of the transmission and the pinion is their relationship to "level". As you said, the ladder bar essentially locks that angle into a solid member. As the rear end pivots upward about the ladder bars pivot point at the crossmember, there will be an insignificant amount of rotation in relation to the transmission angle......but being at a higher point will cause the u-joints to change their working angles more significantly..

Put a magnetic digital level on the end of a 4 foot bar sitting on an angle appx the same as a ladder bar would be. Then move that end upwards 3-4" while the opposite end rests on a stool. See how much the angular reading changes.

Overall, I think you understand whats happening and maybe just stated it wrong........but then I could be the one who is wrong.

 

Yes, the angle is changing in relation to the earth. It is also changing in relation to every other object on the earth and everything above in the sky. Its changing in relation to the motor in the car and to your leg standing next to the car.
But none of those things matter. It only matters how much its changing in relation to the transmission.
We use "level" as a reference to measure that change. We do not use the earth as the reference.

 

Get a better handle on this and we can talk some more if you want.

Since you’re talking about a gravity based angle finder, either weighted pendulum or digital, it’s absolutely referring everything from level ground.

Math with 48” ladder bars ,,,
48” radius equals 301 circumference
360 degrees in a circle.
Each 1 inch of circumference equals 1.19° degrees of the circle.
Follow?
So each 1” of suspension movement equals 1.19° change in the ladder bar.
Follow?
The pinion angle is fixed to the ladder bar because it’s welded. As the ladder bar moves it drags the pinion with it.
Follow ?
That pinion angle changes 1.19° for 1” suspension travel.
That’s it. Not a lot but it changes.

Trust me you could take a chassis, hang it from one corner from a tree and I’ll get the driveline angle’s right. But if you or anyone else is using an angle finder it’s referenced from level ground

 

Thanks for clarifying. I see what you are saying. In my case, I view it as the back end of the trans pointing down while the front of the rear end (the pinion) is pointing up ... obviously I am describing it incorrectly but still managing to get my angles correct

I wondered if that was the case with the OP because, when viewed my way, his angles would be WAY off and would most certainly result in vibration. That's actually why I stated "again, not seeing things in person here..."

Thanks again

 

Fine computer artistry there,
Way better than I could do, look at all the different lines in there by the joints. Fascinating!

However it’s set with both shafts at Zero, the drive shaft at 8° and the ujoint working angles is ____ ?
The industry standard is 3° for great Ujoint life.

For the Ujoint working angles do we take the yoke angle plus the driveshaft angle ? 0 + 8 =8
Or
Do we subtract the drive shaft from the yoke ?
8-0 = 8
Or
Do we throw that asinine illustration away?

Maybe we rotate the engine clockwise 2° and rotate the diff clockwise 2° and see what that does to the drive shaft slope.

 

Assumption or not, if we use that point as a reference, there will be no change in the operating angle of the rear uni throughout full suspension travel range. If the front ladder bar mount points are separated from the front uni pivot point, there will be some change in the rear uni joint orerating angle during suspension cycling....... but it will only be in the region of poofteenths of a degree. I am not talking about pinion angle, drivshaft angle, or whether the whole box of frogs should be referenced from the ground, level, or for that matter, level ground. Simply the angle that the rear universal joint will operate at.

The front uni operating angle will change as usual during suspension cycling, but no more than with any other rear end locating system.

 

Draw it up, I want to see it happen as you say.
I’ll wait. Hell use Pete and Jake’s artwork.

You’re mixing banjo thinking with splayed ladder bars. It’s a little different.
Split your bones and keep closed drive and it doesn’t go well.

 

This?............... or not? The red is the driveshaft.

 

That drawing works if the pivot is the front drive shaft Ujoint . But it can’t be with ladder bars or split bones
the pivot winds up off the front U joint.

actually the geometry is the same for the cowl steer problem.

 

If the ladder bar front pivots/mounts are either side of the uni, and on the exact same horizontal east-west axis as the front uni centrepoint, the drawing will be correct. If the pivots miss this axis by a little bit, there will be some operating angle change at the rear uni during suspension cycling........ but it will not be much. Remember, we are talking only about the operating angle of the rear universal joint, nothing else.....

 

“If the pivots miss this axis by a little bit ,,,”

I believe you’re talking about all of the chassis set ups with ladder bars or split bones.
Even Henry ford and his ball mount didn’t get it exact, nor this build from the front page that got you going on this.
Clearly clearly clearly the pivots are below the Ujoint center line. And guessing where the fore aft placement is ,,, well its probably not exact either.
So whoever built that missed the axis by a little bit. But damn he’s close.



Practice or product or theory vs getting it done- Maybe some can figure out how to get that pivot on exact plane and center both axis while actually building it in real life. I’m not one of them. I get close but miss by a little too.
I’ve not personally built thousands but closings in on 100. I’ve probably had my hands on or face in 1000s and haven’t seen a perfect set up.
Even with custom length bars and custom built front mounts.

Yes it’s 100 percent correct and you’re without fault saying a straight line can be drawn between any 2 points. And that a three point triangle can pivot freely on any 1 corner up to 360 degrees in any direction even. However that is not what ladder bars or split bones are.

There’s 4 points in one plane and then 3 in the other plane 2 of which are fixed and that’s 7 points.
Out of those 7 points 3 of them and the specific 3 up front , one of which is constantly moving, and varying rpm needs to be in perfect alignment and stay in perfect alignment while dynamic with zero run out on 2 shafts. Also accounting for wear and flex and just be perpetual perfect like a unicorn with a winning lottery ticket.
It’s not going to happen in real life as built product.
Your perfect theory without flaw BTW of perfect placement on chassis ladder bars isn’t going to happen.

Yeah but, if it’s it doesn’t miss by a little,,, well if a frog had wings he wouldn’t bump his ass on the ground every time he tried to fly.

For those that have achieved this level of perfection, I bow to you and ask that you teach me how.

 

Yep, essentially that is what I said.
If the front pivot is perfectly aligned there will be no rear uni angle change. (Perfect scenario / simple geometry)
If it is off the mark the angle will change, but not by much. (Real world / best we can achieve)
Thanks for concurring.

Here is a good little read.
https://www.jalopyjournal.com/forum/threads/rear-suspension-ladder-bar-question.1083237/page-2
Posts #44, #45 and #46 have especially good info, and hey @31Vicky with a hemi , one of those posts is yours.......

 

I have a good handle on it but I try not to be arrogant and tend to stick to objectivity. Basic geometry isn't that difficult.

I prefer digital but I'm also familiar with calculating angles (trig) when that's not available. Have done it plenty of times. Still have my little trig book that I got as a machinist apprentice. That being said, while the earth isn't level in general, usually someone works from an area which they "consider level" because they don't have a controlled and calibrated level surface to set their car on. Like "you" said below, you could hang one corner of a chassis from a tree and get it right if you know how. The point simply is that not everyone has a level garage floor or a level driveway to work from .........so they have to use what they have. When they place their engine in the vehicle they have to determine what angle they want the eng/trans to sit. We'll say 3 degrees. At this point the person is going to use some type of angle finder rather than measurements and calculations from the ground.

Then when they install the rear end, they will select an angle that is complimentary to the established engine angle. Normally if the engine is showing down 3 degrees, the rear end should be somewhat less..........so that as torque is applied to the engine and the front of the pumpkin rises, its still not overcentering the engine angle/u joint angle.. When someone adds certain forms of traction device, they limit the ability of the rear end to "wrap" up.

Now as you say, with the ladder bar, as it rotates about the pivot point its angle will change........but what you aren't saying is that the change to the pinion angle will be "downward" as opposed to the "upward" rotational movement when leaf springs wrap under applied torque. Also the pinion reside appx 1 ft ahead of the end of the ladder bar and is only moving in a 3' arc instead of 4. The appx 4 degree rotation of the pinion will be less (appx 3 deg) and the rotation will be in the downward direction even though the whole rear end is moving upward, which helps the situation. So it should have a positive effect on the driveline rather than the implied notion that it would compound driveline angle problems. Also, this would only be happening when the suspension is fully compressed, so I think we can agree that full compression is not going to be happening most of the time..........so again either a minimal or even a positive effect.

As I explained above, the change will have a positive effect on driveline angle instead of compounding it......so the result is actually a positive situation. Another point here is that "level" is an imaginary point taken from the earth in general, not from a specific area of the earth where you happen to be parked. Flat is not always level, but level is always flat.

Maybe if you are measuring from the ground at the Utah Salt Flats.....but the best way to find level is with a reference gage that is calibrated. Ever wonder why water on a garage floor often runs off instead of just sitting in place? I remember watching as machinery was installed at our factory, and inspection equipment was put in place to verify the parts we made, I never saw any of the installations done measuring from the earth........they all used some form of "level" to properly install the stuff..........and that was before digital stuff became even easier. Still have a "precision" level like the ones used by the machine installers in one of my tool boxes.

So lets give it a rest and try to work toward a solution rather than finger pointing.

 

I was resting,,,
But You can have the last word while I watch cartoons. It’s a good one even if your not a Rick and Morty fan

 

Every time there is a driveshaft thread......... YAHOOOOO.

 

Since you said I get the last word..........I simply tried to point out that the simplest way to establish the relationship between the transmission and the rearend is with a digital level which these days can be purchased rather cheaply and just happens to give very precise readings very quickly. In many years past, they were not available and there were precision bubble levels and slightly less precise protractor type levels used. In any instance, the normal way to adjust the position is by starting from a a "known" level or with a tool that shows level and any deviation from level. If you feel that is an excessively technical way to look at this, then I'm happy with that. Go back to sleep now.........

 

Seemingly arrogant if you ask me ^ ^^^’

Get a better handle on this and we can discuss it further if you want .

Not arrogant ^^

Here we go,,,

I don’t have time for this or you now, but I will. And come prepared.

#1 thing you need to be aware of
This is discussion of automotive chassis.
Automotive chassis set on tires.
Tires mounted to a chassis are supposed to be on the ground.
We’re going to set the chassis up statically so as it traverses the terrain and navigates topography it’s retains at its optimal set up.

2nd thing -
If you want to move to discuss drive line angles for such things that are designed to remain static and definitely not level such as sloped conveyor feed, jack shaft assemblies, or or something of that nature make sure you can keep up.

 

Not going to take your innuendo seriously, its not helping the OP any which is supposed to be what we are tryijng to do.

Actually the question by the OP was about his pinion angles relationship with his transmission angle, not his chassis.

So I really don't know where you are going with this. And I don't care. Just remember that while the cars tires do set on the ground normally, establishing the Pinion/Trans angles is usually independent from the chassis stance unless some extreme set-up is being used. There is another thread on here right now where a fellow mentioned placing his engine in a level position because he feels it looks better that way. He has his driveline working just fine .
He could remove the engine mounts, tilt his chassis in a rake, and make new mounts to compensate......and it should still work the same.He could put HUGE tires on the rear of the vehicle.....and the pinion to trans relationship would not change. The OP also stated that he is using a digital level, not the ground for his reference.

....................................................................................................Yep, no arrogance here ^^^^^^^^^^^^^^^


Actually, I don't care to continue. This is going nowhere and no longer objective.

 

Exactly make sure you can keep up !
And by all means let’s stay on the OP issues.
Deyomatic is the OP.
He’s obviously talking about his TRANSVERSE leaf spring AND his ladder bars

Here you go rambling on about spring wrap in
LONGITUDINAL twin springs.
Complete off the OP statements or concerns.

So your not even sure what springs are in deyomatics car ,,,
Yeah make sure you can keep up!

There’s a theoretical idea that’s absolutely impossible to achieve,,,
it goes like this. if ladder pivots could be perfectly aligned with the pivot of a U joint on two axis while spinning there would be no change in the rear U joint operating angle.

Here you go Rambling on about things ,,,, again!
One of your statements was the pinion angle is related to the engine angle…and it is definitely not. but here you’re saying something different than your statement anyway.
Now pay attention and please double check my math. I’ll type slow
Once the differential housing ( that contains the pinion) is welded to the ladder bars the relationship of the pinion to ladders bars does not change in motion.
However any movement of those ladder bars in the chassis changes the pinion angle. Even by your own statements you’re contradicting yourself.
Yeah keep up.

Eki, You’re obviously not an a stupid man. I enjoy many of your posts and some of them are pretty damn good. You obviously have some information albeit lacking and know a bit about drive line angles.
Beyond all reasonable doubt you’ve easily proven that you do not understand what you do know about them. You could learn, you could be an expert, but until then other people would be way better off learning things that you’re good at. This subject my friend is not one of them.

 

NOPE..........that's just what you assumed I meant, but not what I actually said.

If you reread what I wrote, you will see that it was an explanation of the fact that its normal for a rear end (pinion) to (attempt to) rotate upward when torque is applied.
I referenced a leaf spring suspension. I DID NOT reference a "longitudinal" leaf spring or "leaf spring wrap up" suspension as you stated. All rear ends normally used in the cars we mess with want to rise when torque is applied. It doesn't matter if the leaf springs are mounted longitudinally or transversely. To prevent that rotation, some type of locating device must be used, and it often also helps locate and constrain the rear ends movement.
The OP did not initially state that his was a transverse spring, but did mention it was not the original frame and also referenced a "4 link" in his posts. His picture did not show what type of suspension he had. It really doesn't matter if it was longitudnal or transverse leaf ( as he did mention in a later post)........when torque is applied the pinion will try to rotate upwards and some type of limiting device must be used to control/limit that rotation.

In general use, most cars employ parallel leaf spring set ups although evolution has added quite a number of coil or coil over setups. When using parallel leafs it is not unusual for the builder to rotate the pinion angle so that when it rotates under torque, its operating angle while under torque rises and works better with the transmission angle.
Its commonly referred to as the the "pinion gear trying to climb the ring gear". In severe cases, this torque actually causes the whole car to rise and a wheelie ensues.
Again, it does not matter what type of leaf spring or coil spring or whatever, for every action there is an equal and opposite reaction. EVEN If it was a coil over set up, like many people use these days, the pinion rise still needs something to control it.

Video: How Do Traction Bars Work to Control Axle Wrap & Wheel Hop(onallcylinders.com)

As stated above, pinion wrap will need to be controlled no matter what springs are used.

Huh? So we can just mount the engine at any angle and it won't affect anything ?
Watch the video below.
Driveshaft Angle and Phasing - Bing video

YES........it does. The question is whether the combination of relationships between all the moving parts will be sufficient to be detrimental to anything. As I said in an earlier post, the movement upward of the "whole" rear end is in an arc. With transverse leaf suspension, the linear movement of the springs is in disagreement with the circular movement of a ladder bar. There is some give there due to rubber bushings. If the ladder bar is able to rotate upwards about its pivot point, the whole rear end will move higher but the angle of the pinion will be different and more downward. This tends to offset the rise of the whole rearend in relation to the transmission. No its not exact, but they both happen at the same time and are somewhat offsetting.


OK, now I've had my say. We disagree. Like you, I would like to remain friends and I enjoy reading many of your posts and find good content in them.

 

When I have problem's, I make adjustment's until the problem is fixed... Or until it's worse than it was when I started...

 

I use a similar approach at work.
“Well it’s broke, I can’t really break it more”

 

I tried a variation of that
“Well I'm broke, I can’t really get more broke” [unfortunately that was proven wrong]

 

Been there, done that!

 

So easy to understand, but so easily missed.

In this configuration, all points move, within some constraints, as they are attached to each other. The only way that the u-joint on the pinion not to move is to either not have one, or to not move the vehicle.

Fully rigid swingarm, with zero lateral articulation, or parallel ladder bars (assuming no flex).

That would make for a miserable ride, and does for so many that choose that mistake.

 

Exactly!
It’s just not ever going to happen in real life.

If arguing from a platform of purely chalk board mathematics and geometry . it’s true for the most part.
but in practice on a chassis it ain’t happening, ever.