Hot Rods Pinion angle...I know.. "AGAIN?", Really??

I guess after all the threads I've checked out I've never found this exact answer.
I have a model A coupe with an 8" Ford Maverick rear end, parallel 4 bars and QA1 coil overs 125 lb springs if I remember correctly.
When welding on my 4 bar brackets onto the rear end, do I weld them on straight forward to where the pinion angle is at zero degrees or do I weld them on straight forward to where the pinion angle would be at 3 degrees up.
One more question while I'm at it, all the rear end brackets seem to made for 3 inch axle shafts and an 8 inch is about 2 3/4" or so. What have you done to make up the difference as far as the gap between the bracket size and rear end size. Did you use a shim of some sort?
Any pics anyone would have concerning anything to do with this whole 4 bar mounting process would be very helpful especially the bracket shims.
Thanks, XtechX

 

If the trans is down 3 you want the pinion up 3. If the trans is down 2 you want the pinion up 2 see how that works? You want the pinion to be running parallel with the tail shaft of the trans so the u joints are working the same angles. Of course there are some exceptions but this the basic rule. As for the brackets yes, you want them to fit the housing tubes nicely. It sounds like you are gonna need better fitting brackets. Which should be available from numerous sources.

 

So do I set the brackets so it makes the pinion match the trans output or do I set it at zero and use the 4 bars to set the pinion angle?

 

Dont wanna hijack this but as Russco
mentioned above about the 3 up and 3 down situation, which I understand completely!
*My question is what if your pinion is higher than the transmission output shaft? Under throttle the pinion will rise, pushing it further up out of the 3degrees, lets say up +2 for argument sake...So now it would be 3 at trans and 5 up at pinion..?
(I would love to know if ANYONE knows if there is a rough # for angle of rise).
Don’t you start to push the envelope of the rear driveshaft for driveline vibration or u-joint failure?
In my scenario the pinion is higher than the trans output shaft is there any benefit to putting things closer to 1degree so when things rise on throttle the angle changes but it is now a little less harsh, say 1 at trans and 3 up on pinion. The angles would be different but at least lower (3 is better than 5)? Or am I taking this to the extremes only in my mind, I do also think once you get off the pedal a bit the pinion will come back to “rest”.
This is for a hotrod for the streets not a full race car.
Please help school me also....

 

I would put the thread adjustment in the middle to allow for any adjustment you might make. Yep, a dead horse on angles.

 

With a 4 bar, the pinion won't rise, and the reason for the angles to be parallel is because 99% of the time the car is not under acceleration and the u joints are in phase. Truth is, you can set the angle any way you please if you don't mind the annoying hum, (vibration) in your ass and replacing u joints regularly..........

 

This is a settled issue. Stop creating new threads, and just do a search.

You are beating the dust of the bones of the horse that long ago died, and decayed.

 

I’ve seen different angles suggested for different rear supsension types to allow for the rear suspension rotation under hard acceleration, (primarily for drag racing applications) I have played around with setting mine up slightly off to compensate for rotation. In the end for a street car I really couldn’t notice the difference.
Leafsprings will move quite a bit under acceleration (and deceleration) if no traction devices like Cal Tracs or slapper bars are used, while ladder bars and four links move very little if at all.
The ujoint doesn’t know or care which end of the drive shaft is above the other they just care that the working angles are the same (or as close as you can get them) at each end. And yes there are some very good and detailed threads covering all this already. Check out how much the angle changes in this video

 

....and if I might take a slight liberty with your signature line
"Those who cannot remember the past are condemned to repeat it."
-George Santayana
"Those who are ignorant of the past are condemned to claim it never happened."
-Me
"Those who do not use the search function are condemned to open new threads to rehash old topics."
-BanditBilly

 

Amen, brother!

 

That vehicle needs a device, or devices to control axle wrap.

 

Thanks a ton Russco, I’m a visual guy so the vid really helps me lock it down in my mind. MUCH APPRECIATED!!!!

 

Well, you got hijacked and no one answered your question. It is my opinion that the 4 bar links should be all the same length, so as not to cause a pinion angle change or induce any twisting force on the axle housing. I would install the 4 bar bracket with pinion up 3 degrees if that is what your trans angle is. Leave yourself room to adjust both ways on the links.

 

remember ! set the rod ends with about 3 to 5 threads showing past -outward -of the adjuster nuts-& try to make all 4 bars -identical lengths-on a street car i like the rubber-poly type of rod -ends for street -quiet & very tuff ! the hiem type will beat you -to death !!good luck & let us know where you went ?

 

I like to show the attached picture from the 1960 Chevy repair manual.
The pinion is down.
Every production car I have ever looked at has the pinion down.
The reason they do this is to keep the joints working angles closer to the same with suspension movement.
As you surmise, having the pinion up makes the joints working angles get more different as the suspension moves.
The design of having the angles parallel works but it is bad if you have suspension travel.
The rear axle usually rotates about a point forward. Having the pinion down keeps the working angles closer together.
The parallel design is one solution to the problem but sure is not the best one.

 

Two-piece, or more, shafts have different dynamics.

 

The only objective with the parallel axis design is to get the working angles the same. The pinion up design has them move apart with suspension movement. Pinion down like the car companies use results in less change.

 

Because the same crap is repeated over and over and over again.
It doesn't work!
It's like dogs eating vomit and puking it up again for the next dog to repeat.

Below is the true visual representation of the infamous "Trans 3* down / pinion up 3*"

In the same damn paragraph it contains Equatable verbiage that the "Trans out put shaft and the pinion should be PARALLEL ". No body says there's a change of reference points or directions when they turn their little angle finder around as well as themselves.

That stuff is said, then read and then regurgitated over and over, none of it makes any difference or matters at all. There's also all kinds of horse shit about intakes and carbs being level that makes no difference. Any one searching pinion angles will find a nearly infinite number of statements repeating the same.

What matters and all that matters is the working angles of the U joints should be equal absolute values. The problem is that if the person trying to understand this didn't pay attention in math class they won't get it.

Take for instance the standard "3* Trans down 3* pinion up" nincompoopery and mesh it with the "parallel" garbage and make a level the carb surface horseshit and set up this configuration drivetrain.

It's impossible, and exactly why it comes up often. But if you just happen to know that what's needed is the u joint working angles to be equal and that the deluge of info is nonsense and IF you can ignore it then it's no problem to get the above rolling free of drive line angle problems.

Yep it's been gone over a million and 4 times, to bad the wrong info has been conveyed so often. It's damn near gospel status and although not completely wrong, it fits very very few If any custom or hot rod chassis configurations.

One could take a chassis and hang it from a tree by one frame horn so it's swinging in the breeze without one straight, level, square or solid point of reference to the ground and set up a perfect drive line with working u joint angles.

 

Thank you. You explaned it better than I ever did.

 

I guess I'll go burn my engineering degrees now.

 

Just study the Chevy drawing I posted and figure it out. It is pretty neat once it's secrets come out. Take care and have fun. It really is not world shattering.

 

I guess all of my happy customers are living a lie. I should call them and let them know.

 

31Vicky : Help me to understand your reply...
As long as A & B are equal either of these driveline configurations would work ??

Stan

 

No I could not say that as an absolute.

The u joint working angle of both ends needs to be equal (or very close) in a one piece drive shaft.
Given that the in topview Trans and pinion are parallel with chassis center, yes?
First angle is the Trans output shaft to the drive shaft - a working angle "A"
Second angle is the drive shaft to pinion - a working angle "B"
Remember those angle can be in a single horizontal plane where everything is on center when viewed from the top or multiple planes if there's an offset of center when viewed from the top- engines off set for steering or differentials with offset pinions.

 

Both of these fit the 3* stuff but you'd be silly to build a car like that.



None of these fit ANY OF the 3* stuff and not only work BUT FIT and work better in most custom and hot rod configurations.


Just for shits and giggles,,,
Let's build a few cars
First a hot rod car with no hood sides.
Give it a nice hot rod 4* chassis rake with big and littles
Now set the engine in with the 3* down stuff
How shitty does the 7* angle between engine and firewall look ?
How shitty does the Trans tail look hanging under the frame?
The drive shaft is probably running up hill into a pinion that needs to point the other way

Second a really low riding hot rod or custom
Set the engine in with 3* down stuff but keep the Trans tail at least 5" off the ground.
Does it matter if the front of the engine is too high ?
Now run the drive shaft up hill to the pinion, should be about (tire radius - 3") 10-13"
And now make the pinion nose up down to the rear at the same 3* stuff.
How's it look ?
Brilliant concept right? It follows the 3* gospel but it's an asinine drive line.

Carb surface needs to be level ??
Ok let's take the engine sitting in a chassis with the 3* crap set up perfectly.
Let's take the intake off and bolt on a blower, cool hot rod stuff right?
Ok we got a big problem because the carbs aren't level any more. They are 3* down with the crank center line.
Now what?
Set your hair on fire because it violates the rule?

Ok let's take the engine sitting in a chassis with the 3* crap set up perfectly.
How about we throw a big and little rubber rake on it.
The chassis is setting with a great 4* rake and looks really bad ass.
Well the engine isn't 3* down anymore it's 1* up and the carbs are not level anymore they went up with the engine bolted into the chassis.
Now what?

Set your hair on fire because it violates the rules ?
Send the new shoes back because you can't live lies and violate the rule
Don't do cool hot rod stuff ?
Build stuff stupidly that follows the rules But looks like it's broken?
Don't drive up and down hills so your carbs stay level?

Maybe figure out the rules are not what's important at all, for Pete's sake they aren't even stated correctly. To even attempt to state the 3* down 3* up rule correctly there needs a verse from the hokey pokey in there where you take the angle finder and shake it all about - turn yourself around so now down is up and Up is down and that's what it's all about. The hokey pokey and duck duck goose are still fun I guess.
Its the relationship of the angles that is important.

 

If you review my posts, you will see that I write trans pointing down, toward the pinion, and pinion pointed up, toward the trans, with the chassis set level, irrespective of operational rake.

That is not what was depicted in that picture.

I don't build what is in that picture, and I don't build cars that shake, even past 200mph.

 

My daily driver is 0º/0º, with the pinion slightly above the talishaft.

At the rev limiter, flat-out on (closed course, professional driver) course, it does not shake, in any way.

 

Wow!

 

What might happen on these older cars that get lowered - when a few rear leaves are removed and springs are flattened?
Would it not be the same or even worse?